APPLIED ACOUSTICS SYSTEMS Strum Acoustic GS-1 User manual

USER MANUAL

2
Information in this manual is subject to change without notice and does not represent a commitment on
the part of Applied Acoustics Systems DVM Inc. The software described in this manual is furnished under a
license agreement. The software may be used only in accordance of the terms of this license agreement. It is
against the law to copy this software on any medium except as specifically allowed in the license agreement.
No part of this manual may be copied, photocopied, reproduced, translated, distributed or converted to any
electronic or machine-readable form in whole or in part without prior written approval of Applied Acoustics
Systems DVM Inc.
Copyright c 2008 Applied Acoustics Systems DVM Inc. All rights reserved. Printed in Canada.
Program Copyright c 2008 Applied Acoustics Systems, Inc. All right reserved.
Strum VG is a Trademark of Applied Acoustics Systems DVM Inc. Windows 98, 2000, NT, ME, XP and
DirectX are either trademarks or registered trademarks of Microsoft Corporation. Macintosh, Mac OS and
Audio Units are registered trademarks of Apple Corporation. VST Instruments and ASIO are trademarks of
Steinberg Soft Und Hardware GmbH. RTAS is a registered trademarks of Digidesign. Adobe and Acrobat
are trademarks of Adobe Systems incorporated. All other product and company names are either trademarks
or registered trademarks of their respective owner. Unauthorized copying, renting or lending of the software
is strictly prohibited.
Visit Applied Acoustics Systems DVM Inc. on the World Wide Web at
www.applied-acoustics.com

Contents
1 Introduction 9
1.1 SystemRequirements................................. 9
1.2 Installation ...................................... 10
1.3 Authorization and Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.3.1 Step 1: Generating the Challenge Key . . . . . . . . . . . . . . . . . . . . 11
1.3.2 Step 2: Generating the Response Key and Registering your Product . . . . 11
1.3.3 Step 3: Completing the Unlock Process . . . . . . . . . . . . . . . . . . . 14
1.3.4 Obtaining your Response Key and Registering by Fax or over the Phone: . 15
1.4 GettingStarted .................................... 15
1.4.1 Using Strum Acoustic in Standalone Mode . . . . . . . . . . . . . . . . . 15
1.4.2 Exploring the Factory Presets . . . . . . . . . . . . . . . . . . . . . . . . 16
1.4.3 UsingMIDILinks .............................. 17
1.4.4 Using MIDI Program Changes . . . . . . . . . . . . . . . . . . . . . . . . 17
1.4.5 Using Strum Acoustic asaPlug-in...................... 17
1.5 GettingHelp...................................... 17
1.6 ForumandUserLibrary ............................... 18
1.7 AboutthisManual .................................. 18
English 9
2 An Overview of Strum Acoustic 19
2.1 Chord Detection and Voicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2 Strumming ...................................... 20
2.3 TheGraphicalInterface................................ 20
2.4 SignalFlow...................................... 20
3 Keyboard Layout 23
3.1 LeadandChordKeys................................. 23
3.2 StrummingKeys ................................... 23
3.2.1 Downstroke and Upstroke . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.2.2 Palm Muted Downstroke and Upstroke . . . . . . . . . . . . . . . . . . . 24

4 CONTENTS
3.2.3 Muffled Downstroke and Upstroke . . . . . . . . . . . . . . . . . . . . . . 24
3.2.4 MuteAll ................................... 24
3.2.5 AlternateStrum................................ 24
3.2.6 Playing Individual Strings . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.3 PitchBendWheel................................... 25
3.4 Aftertouch....................................... 26
3.5 ModulationWheel .................................. 26
3.6 HoldPedal ...................................... 26
4 Playing Strum 28
4.1 Auto-Strum Mode and Strumming Keys . . . . . . . . . . . . . . . . . . . . . . . 28
4.2 PlayingwithAuto-Strum............................... 28
4.2.1 StrumDown ................................. 28
4.2.2 ChordChange ................................ 29
4.2.3 Chords and Change of Pitch . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.2.4 Hammer-On and Pull-Off . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.3 Using the Strumming Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.3.1 Down- and Upstroke Strum . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.3.2 Palm Muted Down- and Upstroke . . . . . . . . . . . . . . . . . . . . . . 31
4.3.3 Muffled Down- and Upstroke . . . . . . . . . . . . . . . . . . . . . . . . 31
4.3.4 Arpeggios................................... 31
4.4 SpecificTechniques.................................. 33
4.4.1 Trills ..................................... 33
4.4.2 TremoloPicking ............................... 33
4.4.3 MutedStrum ................................. 33
4.4.4 PartialStrumming .............................. 33
4.4.5 Bass&Chords ................................ 34
4.4.6 StationaryBend................................ 34
4.4.7 PowerChords................................. 35
4.5 UsingMIDILoops .................................. 35
4.5.1 CreatingMIDILoops............................. 36
4.6 ChordVoicing..................................... 36

CONTENTS 5
5 Presets and MIDI maps 39
5.1 Presets......................................... 39
5.1.1 ThePresetLibrary .............................. 39
5.1.2 TheProgramlist ............................... 39
5.2 Playing and Changing Presets . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
5.3 Editing and Saving Presets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
5.4 SavingtheProgramList ............................... 42
5.5 Organizing the Preset Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
5.5.1 CreatingFolders ............................... 42
5.5.2 Copying and Moving Presets and folders . . . . . . . . . . . . . . . . . . 42
5.5.3 Renaming Presets and folders . . . . . . . . . . . . . . . . . . . . . . . . 43
5.5.4 Deleting Presets and Folders . . . . . . . . . . . . . . . . . . . . . . . . . 43
5.5.5 Documenting Presets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
5.5.6 Locating a Preset in the Browser . . . . . . . . . . . . . . . . . . . . . . . 43
5.5.7 Resizing the Browser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
5.6 MIDIMaps ...................................... 44
5.7 Exporting and Importing Presets and MIDI maps . . . . . . . . . . . . . . . . . . 44
5.8 Backuping Presets and MIDI Maps . . . . . . . . . . . . . . . . . . . . . . . . . . 44
5.9 Restoring the Factory Presets and MIDI Links . . . . . . . . . . . . . . . . . . . . 45
6 Parameters 46
6.1 General Functioning of the Interface . . . . . . . . . . . . . . . . . . . . . . . . . 46
6.1.1 TweakingKnobs ............................... 46
6.1.2 Buttons .................................... 46
6.1.3 Drop-down Menus and Displays . . . . . . . . . . . . . . . . . . . . . . . 47
6.1.4 BypassingaModule ............................. 47
6.1.5 ModulationSignals.............................. 47
6.2 TheGuitarModules.................................. 47
6.2.1 TheStringsModule ............................. 48
6.2.2 The Pick/Fingers Module . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
6.2.3 TheHammerModule............................. 49
6.2.4 TheMuteModule .............................. 49

6 CONTENTS
6.2.5 ThePalmModule............................... 50
6.2.6 TheGlobalModule.............................. 50
6.2.7 TheBodyModule .............................. 50
6.3 TheEqualizerModule ................................ 50
6.4 TheMulti-EffectModule............................... 51
6.4.1 Delay ..................................... 52
6.4.2 Chorus .................................... 53
6.4.3 Flanger .................................... 53
6.4.4 Vibrato .................................... 53
6.4.5 Phaser..................................... 53
6.4.6 Wah...................................... 54
6.4.7 NotchFilter.................................. 54
6.5 Reverb......................................... 55
6.6 EditMode....................................... 55
6.6.1 TheStringsModule ............................. 56
6.6.2 The Pick/Fingers Module . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
6.6.3 TheHammerModule............................. 60
6.6.4 TheMuteModule .............................. 60
6.6.5 ThePalmModule............................... 60
6.6.6 TheBodyModule .............................. 61
6.7 PerformanceParameters ............................... 61
6.7.1 ChordDisplay ................................ 61
6.7.2 Chord..................................... 62
6.7.3 Loop ..................................... 62
6.7.4 Strumming .................................. 63
6.7.5 Tuning .................................... 64
6.7.6 PitchWheel.................................. 64
6.7.7 Aftertouch .................................. 65
6.7.8 HoldPedal .................................. 65
6.7.9 ModWheel.................................. 65

CONTENTS 7
7 Toolbar 66
7.1 ProgramDisplay ................................... 66
7.2 MIDImap....................................... 66
7.3 CPUmeter ...................................... 66
7.4 ValueDisplay..................................... 66
8 Audio and MIDI Settings 67
8.1 AudioSettings .................................... 67
8.1.1 Selecting an Audio Device . . . . . . . . . . . . . . . . . . . . . . . . . . 67
8.1.2 AudioControlPanel ............................. 67
8.2 MIDISettings..................................... 67
8.2.1 Selecting a MIDI Device . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
8.2.2 CreatingMIDILinks............................. 68
8.2.3 EditingMIDILinks ............................. 68
8.2.4 DeletingMIDILinks............................. 69
8.2.5 CreatingaMIDIMap............................. 69
8.2.6 EmptyMIDIMap .............................. 69
8.2.7 Defining a Default MIDI Map . . . . . . . . . . . . . . . . . . . . . . . . 70
8.2.8 MIDI Program Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
8.3 LatencySettings.................................... 70
9 Using Strum Acoustic as a Plug-In 71
9.1 WindowSize ..................................... 71
9.2 Audio and MIDI Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
9.3 Automation ...................................... 71
9.4 MultipleInstances................................... 71
9.5 SavingProjects .................................... 71
9.6 MIDIChannel..................................... 72
9.7 MIDIprogramchange ................................ 72
9.8 Performance...................................... 72
10 Quick Reference to Commands and Shortcuts 73
11 Appendix - Lists of Chords Detected by Strum 79

8 CONTENTS
12 License Agreement 86

Introduction 9
1 Introduction
Strum Acoustic GS-1 is a synthesizer dedicated to the emulation of acoustic guitars. The syn-
thesizer is entirely based on the A|A|S physical modeling technology and uses no sampling nor
wave tables. Instead it produces sound by solving, on the fly, mathematical equations modeling the
different components of a guitar and how they interact. This elaborate synthesis engine responds
dynamically to the control signals it receives while you play thereby reproducing the richness and
responsiveness of real instruments.
Strum Acoustic features elaborate modeling of the vibrations of the strings, pick or finger action
and the body of the guitar. Strum Acoustic also includes many functionalities which make it easy
to reproduce the playing techniques of a guitarist on a keyboard. Strum Acoustic includes a chord
detection module and performs automatic voicing of chords. In other words, you play the chords
you know on the keyboard and Strum will voice them automatically, for different musical styles, as
a guitarist would have played them. The picking-hand technique of a guitarist is reproduced by an
auto-strum function, special strumming keys or using standard MIDI loops.
Before discussing the synthesizer in more detail, we would like to take this opportunity to thank
you for choosing an A|A|S product. We sincerely hope that this product will bring you inspiration,
pleasure and fulfill your creative needs.
1.1 System Requirements
The following computer configuration is necessary to run Strum Acoustic:
Mac OS :
•Mac OSX 10.2 (Jaguar) or later.
•G4 733 MHz Processor
•256 MB RAM
•1024 x 768 or higher screen resolution
•MIDI Keyboard (recommended)
•Ethernet Port
Windows :
•Windows 98SE/ME/2000/XP
•PIII 800 MHz
•128 MB RAM
•1024 x 768 or higher screen resolution
•DirectX or ASIO supported sound card
•MIDI Keyboard (recommended)

10 Introduction
Keep in mind that the computational power required by Strum Acoustic depends on the number
of voices of polyphony and the sampling rate used. These computer configurations will enable you
to play the factory presets with a reasonable number of voices.
1.2 Installation
Mac OS
Insert the Strum Acoustic program disc into your CD-ROM drive. Open the CD icon once it
appears on your desktop. Click on the Strum Acoustic Install icon and follow the instructions of
the installer.
If you purchased this software online, simply double-click on the installer file that you have
downloaded and follow the instructions of the installer.
Windows
Insert the Strum Acoustic program disc into your CD-ROM drive. Launch Explorer to view the
content of the CD-ROM and double-click on the installer file to launch the installer.
If you purchased this software online, simply double-click on the installer file that you have
downloaded and follow the instructions of the installer.
1.3 Authorization and Registration
Strum Acoustic uses a proprietary challenge/response copy protection system which requires au-
thorization of the product. A challenge key is a long string of capital letters and numbers that
is generated uniquely for each machine during the registration process. In other words, for each
machine you install this program on, a different challenge key will be generated by the program.
The response key is another unique string of capital letters and numbers generated from the data
encrypted in the challenge key. In order to obtain a response key, you will need to connect to the
A|A|S website and provide the following information:
•A valid email address
•Your product serial number (on the back of the sleeve of your CD or in your confirmation
email for downloads)
•The challenge key generated by the program
Note that it is possible to use the program during 15 days before completing the authorization
process. This period can be convenient if you are installing the program on a computer which is
not connected to the internet. After that period, the program will not function unless it is supplied
with a response key.
In the following sections we review the different steps required to generate the challenge keys
and obtain the response key. The procedure is similar on Windows XP and Mac OS systems.

1.3 Authorization and Registration 11
1.3.1 Step 1: Generating the Challenge Key
After launching the installer for the first time, a pop-up window will appear asking you if you wish
to authorize your product now or later. If you are ready to authorize Strum Acoustic now, click on
the Next button otherwise click on the Authorize Later button. If your computer is connected to
the internet, we recommend that you authorize your product now.
Figure 1: Choosing to authorize Strum Acoustic now or later.
When you click on the Next button, a second window appears asking you to enter your serial
number. Type your serial number as it appears on the back of the sleeve of the Strum Acoustic
CD-ROM. If you purchased Strum Acoustic online, an email with your serial number will have
been sent to you at the address which you provided during the purchase process.
After entering your serial number, click on the Next button and your challenge key will appear
automatically in the next pop-up window.
1.3.2 Step 2: Generating the Response Key and Registering your Product
If your computer is connected to the internet, click on the link to the A|A|S web server appearing
in the pop-up window. This will launch your web browser and connect you to the unlock page of
the A|A|S web server. Enter your email address, serial number and challenge key in the form as
shown below and click on the Submit button.
The next form asks you to provide additional information about yourself including your mailing
address and phone number. This information will be used to register your product. Note that
only a valid email address is required to register your product. We nevertheless recommend this
information be provided to ensure our support team is able to contact you to resolve any future

12 Introduction
Figure 2: Enter your serial number in the pop-up window.
Figure 3: The challenge key appears automatically after entering the serial number.
support issues, and notify you of product updates promptly. This information is kept completely
confidential. Registration of your product will entitle you to receive support and download updates
when available, as well as take advantage of special upgrade prices offered from time to time to
registered A|A|S users. Note that if you already purchased or registered another A|A|S product, the
information that you have already supplied under the same email address will appear in the form.
Feel free to update this information if it is outdated. Click on the Submit button and your response

1.3 Authorization and Registration 13
Figure 4: Enter your registration information on the A|A|S webserver.
key will appear on-screen.
Figure 5: Generation of the response key on the A|A|S server.
If your computer is not connected to the internet, take note of your serial number and challenge
key and proceed to an internet connected computer. Launch your browser and go to the unlock
page of the A|A|S website at:
http://www.applied-acoustics.com/unlock.htm
Enter your email address, serial number, and challenge key, and click next. You will then
receive your response code on-screen as described above.

14 Introduction
1.3.3 Step 3: Completing the Unlock Process
The response key corresponding to your serial number and challenge key will be printed in your
browser window. In order to complete the unlock process, copy the response key and paste it into
the corresponding field of the installer window of Strum Acoustic. If you obtained your response
key from another computer, type the response key by hand in the installer window.
Figure 6: Final step of the unlock process. Enter your response key in the window.
Click on the Next button and a pop-up window will appear informing you that the authorization
process has been successful. Click on the Finish button to complete the process and launch Strum
Acoustic.
You will normally only need to go this process once for a given computer except for some
special cases. On Windows computers your will need to unlock again if:
•You change your computer
•You reformat or upgrade your hard drive
•You change or upgrade your operating system
On Mac OS computers, this will only be necessary if:
•You change your computer
•You change the motherboard of the computer

1.4 Getting Started 15
Figure 7: Authorization has been successful.
1.3.4 Obtaining your Response Key and Registering by Fax or over the Phone:
Should you not have access to the internet, A|A|S support representatives are available to assist
you in the unlock and registration process Monday to Friday, 9am to 6pm EST. You may contact
us by phone at:
•North America Toll-free number: 1-888-441-8277
•Outside North America: 1-514-871-8100
•Fax Number: 1-514-845-1875
•Email: [email protected]
1.4 Getting Started
1.4.1 Using Strum Acoustic in Standalone Mode
The Strum Acoustic comes with a wide range of factory presets right out of the box which amounts
to a huge range of sounds before you have even turned a single knob. As you would expect, the
best way of coming to grips with the possibilities Strum Acoustic offers is simply to go through the
presets one at a time. We recommend that you first start using Strum Acoustic in standalone mode.
•Windows - Double-click on the Strum Acoustic icon located on your desktop or select Strum
Acoustic from the Start >All Programs >menu.

16 Introduction
•Mac OS - Double-click on the Strum Acoustic icon located in the Applications folder.
Before you start exploring the factory presets, take a moment to set up you audio and MIDI
configuration as explained below.
Audio Configuration
Audio configuration tools are available from the Audio menu. The Audio Settings function allows
you to select an audio output device from a list, organized by driver type, of those available on your
computer. On Windows, if you have ASIO drivers available, these should be selected for optimum
performance. Multi-channel interfaces will have their outputs listed as stereo pairs.
•Select your sound card port from the list in the Audio Configuration dialog from the Audio
>Audio Settings . . . menu.
For more detailed information on audio configuration, sampling rate selection and latency ad-
justments, please refer to section 8.3.
MIDI Configuration
MIDI configuration tools are available from the MIDI menu.
•Select your MIDI input device from the list in the MIDI Configuration window available
from the MIDI >MIDI Settings . . . menu.
For more detailed information on Audio and MIDI configuration, MIDI links and MIDI maps,
please refer to Chapter 8.
1.4.2 Exploring the Factory Presets
Factory presets can easily be accessed using the ‘+” and ‘−” buttons in the lower left corner of the
toolbar. These buttons are used to navigate through a list of 128 numbered presets called programs.
The content of this program list can be viewed by clicking on the Hbutton of the toolbar. The
number of the current program used and the name of the associated preset appear on the right of
this button. Programs can also be changed by using the ‘+” and ‘−” keys from the computer
keyboard or by selecting programs directly from the list displayed after clicking clicking on the H
button.
Presets can also be accessed using the browser appearing on the left of Strum Acoustic. This
browser is similar to the browser your operating system generates to display the contents of your
hard disk, or your email program uses to organize your mail and address book. When launching the

1.5 Getting Help 17
application for the first time, this “tree view” will include a destination folder for imported presets
as well as a Presets folder. To open a folder, click on the “+” symbol on Windows or Isymbol
on Mac OS which will reveal the folder content.
The preset library is different from the program list and can be viewed as a repository con-
taining all the presets available to the application. Presets are loaded into the synthesis engine by
copying them from the library into the program list. To load a preset, double-click on a preset icon
(blue knob) or preset name. This will insert the preset into the program list at the position of the
current program. You can also use the arrow keys on the computer keyboard in order to navigate
in the preset list and then the Enter key to load a preset. For additional information on presets and
programs, please refer to Chapter 5 of this manual.
1.4.3 Using MIDI Links
Every parameter on the Strum Acoustic interface can be linked to an external MIDI controller. To
assign a MIDI Link, right-click (control-click on Mac) on a control (knob, button or slider) and a
contextual menu will appear. Select Learn MIDI Link and move a knob or slider on your MIDI
controller to activate the link. To deactivate the link, right-click (control-click on Mac) on the
control and choose the Forget MIDI Link command. Refer to section 8.2 for more details on
MIDI links.
1.4.4 Using MIDI Program Changes
The synthesizer responds to MIDI program changes. When a program change is received, the
current program is changed to the program having the same number as that of the program change
message received by the application.
1.4.5 Using Strum Acoustic as a Plug-in
Strum Acoustic integrates seamlessly into the industry’s most popular multi-track recording and
sequencing environments as a virtual instrument plug-in. Strum Acoustic works as any other plug-
in in these environments so we recommend that you refer to your sequencer documentation in case
you have problems running Strum Acoustic as a plug-in.
1.5 Getting Help
A|A|S technical support representatives are on hand from Monday to Friday, 9am to 6pm EST.
Whether you have a question on Strum Acoustic, or need a hand getting it up and running as a
plug-in in your favorite sequencer, we are here to help. Contact us by phone, fax, or email at:
•North America Toll Free: 1-888-441-8277

18 Introduction
•Worldwide: 1-514-871-8100
•Fax: [phone]
•Email: [email protected]
Our online support pages contain downloads of the most recent product updates, and answers
to frequently asked questions on all A|A|S products. The support pages are located at:
www.applied-acoustics.com/support.php
1.6 Forum and User Library
The A|A|S community site contains the Strum Acoustic user forum, a place to meet other users
and get answers to your questions. The community site also contains an exchange area where you
will find presets for your A|A|S products created by other users and where you can make your own
creations available to other users.
http://community.applied-acoustics.com/php/community/
http://community.applied-acoustics.com/php/forum/
1.7 About this Manual
In the next chapter, the general functioning of Strum Acoustic is presented. Chapter 3 describes
the special keyboard layout used to play Strum Acoustic. Playing techniques are then presented in
chapter 4. Chapter 5 explains how to use the application browser and how presets and MIDI maps
are managed. In Chapter 6, the different modules and controls are reviewed in detail. Chapter 7
describes the different functionalities available from the toolbar while Chapter 8 explains the dif-
ferent functionalities related to Audio and MIDI and their settings. General issues involved in the
use of Strum Acoustic as a plug-in in different host sequencers is covered in Chapter 9. Finally a
list of available commands and shortcuts is given in Chapter 10.
Throughout this manual, the following conventions are used:
•Bold characters are used to name modules, commands and menu names.
•Italic characters are used to name controls on the interface.
•Windows and Mac OS keyboard shortcuts are written as Windows shortcut/Mac OS shortcut.

An Overview of Strum Acoustic 19
2 An Overview of Strum Acoustic
Strum Acoustic is a synthesizer which was designed with the goal of enabling keyboard players to
easily create realistic guitar tracks. This is a task which is usually difficult to achieve due to the
very different nature of these two types of instruments. Strum was therefore designed to reproduce
not only the sounding mechanism of a guitar but also the main elements of the playing technique
of a guitar player.
Very generally playing on a guitar can be described in terms of fretting hand (usually left hand)
and picking hand (usually right hand) techniques. The fretting hand is used to fix the chords or
notes played on the different strings of the guitar while the picking hand is used to set the different
strings into vibration and therefore play melodies or strumming patterns. In Strum, these functions
have been integrated into a chord detection, voicing, and strumming module.
2.1 Chord Detection and Voicing
Chords played on a keyboard and a guitar share the same name but are played or voiced differently.
Because of the tuning of the strings on a guitar, the notes of the chord are not usually played
in the same order as on a keyboard and the range of the notes is usually different, notes may
also be repeated. Furthermore, the same chords can be played in different positions on the guitar
depending on the playing or musical style. This specific way of playing chords on a guitar is very
characteristic of the tone and sound of the instrument. It is therefore very important, in order to
obtain a realistic guitar sound, to play chords as a guitar player would rather than how they are
played on the keyboard.
The voicing of chords for the guitar is performed in two steps by Strum. A chord played on the
keyboard is first interpreted by the chord detection module in order to determine which chord was
played on the keyboard. Strum then finds a guitar voicing corresponding to this chord. In other
words, Strum finds how a guitar player would have played this particular chord.
When chords are played on the keyboard, the order of the notes above the root is not taken
into account by the chord detection engine. This implies that you can play the chords as you know
them on the keyboard without having to know or learn special voicings used by guitar players. For
example, you could play chords in close position with the left or right hand, you could also play
the root with the left hand and the rest of the chord with the right hand or play the chords with
the notes spread across both hands. Strum will take care of finding the right voicing and playing
position on the guitar depending on the settings of the chord type and playing position controls as
described in section 4.6
The name of the chord detected as well as the specific voicing chosen by Strum is displayed in
the fretboard located in the lower portion of the graphical interface. Note that the voicing chosen by
Strum varies depending on the chord type chosen by the user as is described in Section 4.6. Strum
will try to detect a chord as soon as three or more keys are depressed on the keyboard. Otherwise
Strum will assume that a melody or interval is played. Please refer to section 11 for a list of the
chords detected by Strum.

20 An Overview of Strum Acoustic
2.2 Strumming
On a guitar, notes and chords are triggered by the action of the picking hand (usually right hand).
The resulting sound is very typical of a guitar as the guitarist triggers the strings sequentially, more
or less rapidly, with an up and down motion of the hand. Strings can also be played individually,
in different order, to create arpeggio patterns. Different sonorities can be obtained by damping
or muting the strings either by applying the picking hand on the strings near the bridge (palm
muting) or releasing the pressure on the notes played with the fretting hand (scratching) while
strumming. Using these different types of hand motions and techniques, the guitarist can create
complex melodic and rhythmic patterns. In Strum, these different effects can be achieved through
a strumming module which is controlled by special strumming keys or MIDI loops as will be
explained in more details in Chapter 3, 4 and 6.
2.3 The Graphical Interface
The graphical interface of the instrument is divided in three sections. From top to bottom on the
interface one first finds the output effect section which is used to shape the final sound of the
instrument. This effect section includes and equalizer a multi-effect module with sync capabilities
and a reverb.
The middle guitar-shaped section of the interface is where all the parameters controlling the
synthesis engine are located. The different control parameters refer to the strings, the pick and its
interaction with the strings, the action of fingers on the fretboard and the body of the guitar. This
section has seven different views. The main and simplest one (All)is used to display parameters
acting on the six strings of the guitar while the other six views reveal parameters for the individual
strings.
The bottom part of the interface is centered around a fretboard where the chords detected and
the specific voicings chosen by Strum are displayed. This section of the interface also includes
parameters determining how the voicing and strumming is performed by Strum, a MIDI loop player,
tuning parameters and controls determining how signals from some standard MIDI controllers are
interpreted by Strum.
2.4 Signal Flow
The general signal flow of Strum is presented in Figure 9 and illustrates schematically how the dif-
ferent modules in Strum interact. From left to right, the synthesizer first includes a chord detection
module which parses the MIDI signal it receives and determines the chords played on the keyboard.
This information is then sent to the voicing engine which, taking into account how a guitarist would
actually play the different chords, determines which notes are played on the different strings of the
guitar. The corresponding information, for each of the six strings of the instrument, is then sent to
a triggering or strumming module which generates an excitation signal for each of the individual