midiphy LOOPA User manual
REQUANTIZING DIY MIDI SEQUENCER
USER MANUAL
Version 2.05 2019-11-14
written by Hawkeye/Peter Knoblach
www.midiphy.com
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Contents
1. Welcome to LoopA! 2
2. Features 3
3. Quickstart 4
4. User Interface Overview 5
4.1 Graphical Display 6
4.2 Encoder knobs 6
4.3 Status LEDs 7
4.4 Keys 8
5. The SHIFT Function 9
6. MENU Usage and LoopA Screens 9
6.1 SETUP Screen 11
6.1.1 Editable Setup Parameter List 11
6.1.2 Defining Named User Instruments 12
6.2 MIDI ROUTER Screen 13
6.3 MIDI MONITOR Screen 14
6.4 DISK Operations Screen 14
6.5 TEMPO Screen 15
6.6 MUTE Screen 16
6.7 CLIP Screen 17
6.8 NOTES Screen 17
6.9 LIVEFX Screen 19
6.10 TRACK Screen 20
7. Live Performance Modes 21
7.1 Live Transposition Mode 21
7.2 Live Beatloop Mode 21
8. Acknowledgements 22
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1. Welcome to LoopA!
The midiphy LoopA is a small but powerful DIY requantizing MIDI sequencer with six fully
independent MIDI tracks and six scenes for a total of 36 MIDI clips. A crisp graphical OLED
displays noteroll information along with powerful live performance tools such as live note
requantization, time-based sequence slicing (beatlooping), live transposition, and
real-time effects that tap into your creativity!
If you have a soldering iron and mid-level DIY experience, it can be built in a few evenings.
An extensive build video tutorial will cover each build step.
The LoopA comes in two case variants - a cheaper but sturdy full acrylic variant, and a “pro
variant” proudly made by Hallik Engineering.
The LoopA is small enough to take everywhere and could be powered by a USB
powerbank. Boot-up only takes a few seconds and then it is ready for your next live
session! Enjoy!
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2. Features
●MIDIbox/FreeRTOS (real-time operating system) STM32F4 microcontroller-based
application resulting in minimal MIDI jitter/latency
●Responsive and optimized UI for an easy-to-use workflow with a fast learning
curve: it is ideal for recording concepts/ideas in your studio and for live
performances on stage
●Holds 36 MIDI clips in a matrix of 6 tracks (horizontal) and 6 scenes (vertical)
●Clips contain notes recorded with their original timing, allowing for nearly
unlimited polyphony and unquantized storage of about 10 000 notes per session
(polyphony is naturally limited by MIDI throughput).
●Overdubbing (adding notes) without erasing existing notes (looper approach)
●Dynamic requantization of notes at any time (including during recording) and
real-time application of other LiveFX such as quantized swing and note-skip
probabilities
●Clip scrolling, clip length changes, clip zooming/stretching and note transposition
at any time (including during recording)
●Two performance modes with a dedicated knob for live transposition and
"beatloop", offering different sequence-scrambling time progressions that can
completely alter a rhythm or melody line while keeping the harmony and sequence
runtime identical to the unaltered version
●Manual sequence scrubbing/time scratching with a dedicated knob
●Dedicated scene progression knob, launching six new clips for song progression
●Data entry with push-to-accelerate rotary encoders: pushing the VALUE knob while
turning will expedite changes, useful e.g. for moving a note many steps or
transposing by many semitones
●High-speed two-key "muscle memory" menu navigation and shortcut SHIFT
functions for direct clip launching/track mute/ track unmute access from any screen
●Dedicated clip COPY/PASTE/DELETE keys
●Three DIN MIDI OUT ports and two DIN MIDI IN ports allow direct connectivity of
most classic MIDI gear
●Four virtual USB MIDI IN/OUT ports to drive VSTs/software synthesizers and
connect to your DAW
●Graphical OLED offering instant live feedback on all operations such as
transposition, note probabilities, beatloops and more
●Integrated note editor for editing your sequences without a computer/mouse and
to quickly correct recording mistakes
●Full-sized SD card used to store sessions and for data backup
●Light-weight design and a small case fits into any backpack and can be portably
powered for hours using a standard USB powerbank
●Very quick boot-up times and automatic last-session recall: continue with your work
exactly when inspiration strikes and not after a required operating system software
update :-)
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3. Quickstart
The following steps get you jamming pronto!
If you get stuck somewhere, please read through the “Menu Usage and LoopA Screens”
chapters. These describe every action on each screen in much more detail.
1. Insert a FAT32-formatted SD card into the SD card slot to avoid the diagnostics
mode, which is mostly useful to test hardware functions during the build.
2. Attach your LoopA to your favourite synth (synth MIDI OUT to LoopA MIDI IN1 and
LoopA MIDI OUT1 to synth MIDI IN)
3. Attach a USB B cable to power up your LoopA (you could use a mobile USB charger,
a USB power bank, or just a USB port from your computer)
4. After starting up LoopA, the first track is selected and unmuted (the upper-left key
is illuminated blue-green = cyan) and ARM is activated (2nd key in the lower row is
illuminated red), we are thus already set up to record a sequence on Track 1
5. Press and hold the MENU key (it might be labeled with a “burger symbol” icon) and
push the lower rightmost key to access the TRACK configuration screen, then
release both keys, and you see the TRACK screen.
6. Push the second upper-row key to activate the “MIDI Output Channel” selector and
use the VALUE knob to choose the MIDI channel of your synth
7. Using the Menu, go back to the MUTE Screen and press RUN/STOP to start the
sequencer. The time cursor starts moving, the current track (step or 16th
note-equivalent) positions in the lower part of the display are updated
8. While the sequence is running, play a few notes, try to match the blinking beat LED
on the RUN/STOP key - when the sequence loops, you should hear the recorded
notes in (currently) unquantized playback. If you are unhappy with your current
recording, you can press DELETE (lower right key) at any time to start over.
9. Use the lower-left track knob to choose a different active track and watch the blue
active-track indicator move across the top six keys. Potentially adjust the output
MIDI settings in the TRACK screen as before.
10. Repeat recording a secondary sequence (e.g. a bassline), which will be stacked on
top of the playback of track 1.
11. At any time, have a look in the NOTES, CLIP and LIVEFX screens to modify your
recording - here you could delete or modify single notes, transpose the whole clip,
requantize, apply swing and randomness, change the length of your clip, change
the playback speed of notes, time-scroll notes and do many other things! :)
12. Attach more synths (also software synths can be directly driven via the virtual USB
MIDI ports) and set them up in the TRACK screen. The “live forward” feature there
allows to forward any notes you play on your main keyboard to the configured MIDI
OUT port/channel of the currently active track, so you could listen to e.g.
rackmount synths when using a separate MIDI keyboard for recording.
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13. With the SCENE knob, you can cycle through multiple scenes. Use the COPY and
PASTE keys to copy clips (that could be then modified or overdubbed) and thus
conjure up a simple “song” when progressing through the six available scenes.
14. Use the LIVE knob to test performance features like live transpose and beatloop.
Push it to cycle through those live performance modes.
15. Push and turn the SELECT knob to scrub (manually scroll the time cursor) through
the sequence (while playback is active).
16. You could also have a look at the TEMPO, SETUP, ROUTER and (MIDI)MONITOR
screens to learn more about your LoopA.
17. If you are lost somewhere, push and hold SHIFT and the HELP key to get context
sensitive information.
18. Once happy with your jam, don’t forget to save it on the DISK screen. If you turn off
your LoopA at any time, your last saved (or loaded) session will be automatically
fully recalled.
4. User Interface Overview
Here is the acrylic case LoopA frontpanel:
The user interface consists of a 256x64 pixel, 16 grayscale-level OLED, four knobs (red)
with status indication LEDs around the upper knobs and thirteen keys (blue) organized in
two rows, the upper keys are often directly associated with onscreen actions of the
currently active screen and the lower keys operate basic functions (e.g. sequencer
RUN/STOP) that are available from every screen.
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4.1 Graphical Display
The display is usually divided into three general sections: a title line providing general
information about the active page; a central section most often showing note data (also
used for MIDI router or setup configuration data); and a footer line, which “labels” or maps
the upper six general purpose keys to actions or settings:
Here the MUTE screen of Track 3, Scene B is displayed, which is currently muted and
mapped to user instrument “Andromed” and the current playback position of this clip is
step 43 of 64. The sequencer is running, the time cursor is about three quarters “through
the sequence” and the lower six tracks are available for muting and unmuting by pushing
the first row of keys.
4.2 Encoder knobs
●SCENE
Selects the currently active scene. LoopA has six tracks and six scenes and thus
stores 36 MIDI clips in memory. The scenes are enumerated from A to F and the
tracks are enumerated from 1 to 6, which can be concatenated to “1A” or similar.
This concatenated number consisting of scene number and track number is
displayed on most pages in the upper-left corner of the OLED.
The nearby LEDs visualize the currently active scene.
●SELECT
Multipurpose knob, but usually selects the active track on many screens. On the
note editor page, it selects the edited note; on the config and router screens, it
selects the active configuration item.
Pushing down the SELECT knob while turning will scrub the playback position,
allowing quick fast-forward or rewinds when the sequencer is running.
●LIVE
Live performance knob. Pushing the knob switches between two performance
modes. The default mode is “live transposition”, where turning the knob will
transpose any channels that are enabled for live transposition. When switched to
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“beatloop”, turning will adjust the position of the playback cursor to repeat or skip
beats/measures. Settings are visualized with the nearby LEDs and if neither
transposition nor beatloop is active, two illuminate center LEDs will indicate a
“zero” effect.
●VALUE
Used for entering command and parameter data. A command/operation is first
selected by pushing an upper-row key, then the VALUE is adjusted with the knob.
For example, choose the “track length” command from the Clip screen, and then
turn this knob to select a clip step length equivalent (e.g. 64 steps).
Pushing the knob knob while simultaneously turning it will usually accelerate inputs
(“EXPEDITE”), but is also useful in certain situations to “lock” the input to useful
increments. An example is adjusting track transposition in the “clip” screen, where
pushing and holding while turning this knob will transpose in octaves rather than
semitones.
4.3 Status LEDs
Both SCENE and LIVE encoders are partially encircled by status LEDs, which probably look
a bit differently (LED sizes and color scheme) in your LoopA, but are arranged in this
orientation:
●The six middle LEDs around the SCENE knob indicate which scene is currently
active. An upcoming later feature will allow the LoopA to cycle between the
default "full-scene switching" mode (which just jumps to a new scene with six new
clips active when you turn the SCENE encoder) and single-clip progression within a
track - the upper and lower different-color LEDs are used to indicate that mode -
described as "ALL" and "TRACK" respectively on the frontpanel.
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●The six middle LEDs around the LIVE knob indicate the parameter value of the
currently active LIVE mode. The upper and lower different-color LEDs are used to
indicate the live mode type (labeled "TRANSPOSE" or "BEATLOOP" on the
frontpanel), which can be switched by just pressing the LIVE encoder.
4.4 Keys
●The upper row of six keys typically controls actions displayed in the bottom line of
the OLED. In many screens, these keys choose parameter/value selectors or toggle
between states.
In the often-used MUTE screen, pushing one of the six keys mutes or unmutes one
of the six tracks (unmuted tracks are also illuminated in green). The currently active
track is indicated with a blue backlit key. Therefore, if a track is both active and
unmuted, this leads to a cyan color mix (green and blue); see track three in the
above picture.
●The lower row of seven keys are per default mapped to these functions (from left
to right):
* RUN/STOP: Start or stop the sequencer
* ARM: Enable recording to the current track
* SHIFT: Press and hold to display shift menu
* MENU: Press and hold to display the page/screen selection menu
* COPY: Copy active/selected clip to memory buffer
* PASTE: Paste memory buffer to active/selected clip
* DELETE: Delete notes on active/selected clip
Most keys perform direct actions. Press and hold MENU or SHIFT to directly choose
the desired secondary action or page/screen. An onscreen keymap then displays
the actions of the remaining twelve keys (see SHIFT and "Menu Usage" chapters).
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5. The SHIFT Function
The SHIFT key provides access to shortcuts and additional screens:
●Hold SHIFT: shows the muted/unmuted state of the current track clips and to what
scene they are assigned (see above screenshot).
●Hold SHIFT + press upper-row keys 1-6: measure-synchronized direct mute/unmute
of any track from any screen. This allows ease muting/unmuting/launching of clips
from every screen.
●Hold SHIFT + press and hold ARM: Display context-sensitive help screen describing
the functionality of the currently active screen
●Hold SHIFT + press LIVE knob: resets the currently active live mode parameter to
zero. E.g. if you are in "live transpose" mode and have transposed a few clips, push
the knob to reset transposition.
You can then push the knob again to revert back to the previous value. Use this to
toggle between a nice transposition or beatloop value and no effect. These
"toggle" buffers are also stored in the session file. So you could save a session with
"zero" transposition, but a nice preset toggle transposition and activate it by
pressing SHIFT + LIVE knob.
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6. MENU Usage and LoopA Screens
LoopA offers a two-finger navigation menu system allowing for quick one-handed
navigation utilizing “muscle memory” shortcuts to access often-used screens.
Navigate to the “Clip Settings” page by pushing and holding the menu key and pressing
the Clip key, then release both keys.
All available pages are displayed on the OLED and the corresponding pressed keys are
backlit in red.
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6.1 SETUP Screen
Within the SETUP screen, basic runtime parameters of the LoopA can be modified.
Changes are directly saved to the SD card file called “setup.txt”, which can also be edited
manually in a text editor. To move an active configuration over to another LoopA, copy this
file to the new SD card root.
In the setup screen, use the lower-left SELECT knob to scroll through the configuration
items and to select an active item. Use the upper-row keys below the OLED to select
parameter values and either simply “toggle” them by pushing the respective upper-row
key (e.g. toggle Beat LEDs “on” or “off”), or if a value is selected, use the lower-right
VALUE knob to change settings (e.g. change the OLED Screensaver activation time).
6.1.1 Editable Setup Parameter List
Here is a list of editable setup parameters:
●System Font: changes the system font from a normal/sharp system font (type “a”)
to a smoother, antialiased system font (type “b”)
●Beat LEDs: when enabled, repurposes the lower-right four key backlight LEDs to
display beat and quarternotes
●Beat Display: when enabled, slightly flashes the OLED display background to match
measure and beat
●Screensaver: activates the LoopA screensaver (a voxelspace mountainscape
scrolling by) after a defined number of minutes
●Metronome: defines a MIDI synth to use as a metronome with a configurable MIDI
port/channel (or a user instrument, see below) and define the notes to be played
when a measure and a beat begins
●MCLK IN/OUT: toggles MIDI clock input and output devices, where DIN are
standard MIDI ports and USB are virtual USB devices. Be careful to not accidentally
create a MIDI clock loopback, which might occur if other devices are echoing the
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MIDI clock back to the LoopA and the receiving input port is configured as the MIDI
clock master
All settings within the setup.txt file can be edited by opening this file on a plain text
editor. Certain sections are not (yet) editable within LoopA itself. The “INSTRUMENT”
entries, for example, are described in the next section.
6.1.2 Defining Named User Instruments
Upon opening setup.txt in a text editor, 32 lines are available to define very helpful “user
instrument” abbreviations.
By default, the user instruments are disabled and enumerated as follows:
INSTRUMENT 0 Synth_A OUT1 0
INSTRUMENT 0 Synth_B OUT1 0
INSTRUMENT 0 Synth_C OUT1 0
...
The INSTRUMENT identifier is followed by the instrument number (0-31), a string of up to
eight characters for the synth or device, and the output port and channel. Named User
Instruments can be assigned to any output port, including USB ports.
Transform these lines by using a computer text editor to reflect a custom
instrument/synth setup. LoopA can therefore use “instrument names” instead of
otherwise cryptic MIDI port/channel combinations:
INSTRUMENT 0 Andromed OUT1 1
INSTRUMENT 1 Dominion OUT1 2
INSTRUMENT 2 MoogLP OUT1 3
INSTRUMENT 3 Anushri OUT1 4
INSTRUMENT 4 ESQm OUT1 5
INSTRUMENT 5 EX8000 OUT1 6
INSTRUMENT 6 K3M OUT1 7
INSTRUMENT 7 uWave1 OUT1 8
...
E.g. in line 2 (“INSTRUMENT 1”), a synth called “Dominion” is configured to use MIDI OUT1,
MIDI channel 2. Once a MIDI channel other than “0” is defined, the respective instrument is
enabled. Always start with INSTRUMENT 0 and never leave a gap between instruments, as
LoopA will stop scanning for further user instruments after encountering an output
channel of “0”).
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6.2 MIDI ROUTER Screen
The ROUTER screen defines up to 16 permanent routing paths between LoopA and any
connected MIDI equipment. For example, forward a MIDI controller connected to IN1
(accepting all channels) to a synth connected on OUT1 and transform the output channel
to channel 1:
MIDI packets can also be forwarded to (or sent from) a virtual USB port (when connecting
LoopA to Windows 10 or Mac OS via USB. Four independent MIDI USB devices are added
and could redirect MIDI traffic around a studio.
The router screen offers “commands” that can be selected with the upper-row keys
directly below the OLED:
●Select: Select currently active “route” (also select routes by turning the SELECT
knob).
●IN P: Choose the input port of the active route (IN1-IN4, USB1-USB4). Only MIDI
packets arriving on this port will be forwarded to the configured MIDI output
●IN Ch: Define the input channel of the active route (1-16 or “All”). If a specific
channel is chosen, only MIDI packets on this channel will be forwarded to the
configured output.
●OUT P: Define the output port of the active route.
●OUT Ch: Define the output channel of the active route. If a numeric value is chosen,
the packet is sent only on this destination channel. If “All” is selected, the input
channel number will be used (and is not modified).
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6.3 MIDI MONITOR Screen
The MONITOR screen shows current MIDI traffic from an interface perspective as well as a
short hexdump log:
The above image displays outgoing SysEx traffic on USB1, with three log lines of MIDI
packets sent at the timestamp 11236 (seconds), 781 (milliseconds). The output port is the
USB1 virtual MIDI port (-> arrow) and the hexidecimal string is the actual transmitted data.
6.4 DISK Operations Screen
Save and load Sessions to/from SD card using the disk operations screen:
Scroll through the enumerated sessions with the lower/left SELECT knob (accessed by
number). Upper-row key #2 saves the current session to disk, upper-row key #3 loads a
session from disk (if it is present), and upper-row key #4 initializes a completely new
session, deleting all track and note data.
LoopA will remember the last session loaded or saved upon restart.
Copy the relevant files in the SESSIONS directory on the SD card to backup sessions.
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6.5 TEMPO Screen
Controls the current playback speed and configures a MIDI metronome for a recording guide
or click track:
Press upper-row key #1 to select the current BPM to be modified with the VALUE knob.
Tip: push and turn the VALUE knob for accelerated speed adjustments.
The FASTER and SLOWER commands modify the tempo linearly (and slowly), while the
keys are pressed.
The METRONOME (Metron.) switch activates a midi metronome that plays different notes
at full measures and at beats. Configure the metronome in the SETUP screen: define which
output port the MIDI metronome notes are sent to and which notes should be played
when a full measure or a full beat is reached.
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6.6 MUTE Screen
The MUTE screen could be considered the most important screen of the LoopA. If clips in
the CLIP/NOTES/LIVEFX screens aren’t being modified (see below), the MUTE screen
provides a good overview of the sequences and allows clips to be quickly recorded, muted
and unmuted:
The above screenshot displays a 64-step sequence with stored note data track 6, scene "E",
shortened to “6E”. The output port is USB4 MIDI port, channel 8.
The six upper-row keys launch/unmute clips of the currently active scene or stop/mute
them again. Muting and unmuting is always synchronized to a measure, so can be
"pre-unmuted" in advance and the clip will be launched with perfect timing.
Recording a sequence is most comfortable from the MUTE screen, as the active track is
easily chosen and (also visualized by the blue upper-row key and also the inverted
sequence position display; see the screenshot above). Press ARM and record any set of
notes with a MIDI keyboard, MIDI drumpad or another instrument.
The lower six number slots show the current sixteenth-note-equivalent playback positions
and clip lengths for all six LoopA tracks. A display of 09:64 would mean that playback is at
step (or sixteenth note) 9 of a total clip length of 64 steps (or sixteenth notes).
The top-left of the mute screen displays the currently active track and scene. If the LoopA
is armed, notes will be recorded to this track within the shown scene.
In the center top line, the output instrument of the currently active track is displayed. If
the track was set up to use a user instrument (see chapter: SETUP Screen), a custom
instrument may be displayed (e.g. "ANDROMED"). If not, the MIDI output port and MIDI
channel are displayed instead (e.g. USB4 #8).
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6.7 CLIP Screen
The CLIP screen configures/modifies all of LoopAs 36 stored clips.
The active clip is displayed in the top-left corner (e.g. 1A corresponding to track 1, scene
A). The following operations are available on the top row of keys:
●Key 1 (Len) allows to set the clip length. The length can always be reconfigured
without losing notes, even with the sequencer running. Available clip lengths are 4,
8, 16, 32, 64, 128 steps.
●Key 2 is currently without function but reserved for the clip type for a later LoopA
revision.
●Key 3 (Trn) transposes the whole clip. Tip: when this operation is active, press the
DATA knob and turn to transpose full octaves. This is handy during live
performance.
●Key 4 (Sr) scrolls the track notes forward and backwards,, wrapping around at both
ends.
●Key 5 (Zoom) zooms in the notes. For example a zoom of 0.5 speeds up the
sequence by a factor of 2.
●Key 6 (Freeze) will reset all clip parameters to zero while keeping all notes in their
current place. It will also delete "offscreen" notes (e.g. if the sequence length was
reduced). Use this command to define an order to otherwise unordered chained
transformations. Example: there is a difference between scrolling, freezing and
changing the zoom level to first changing the zoom level, freezing and afterwards
scrolling.
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6.8 NOTES Screen
The NOTES screen allows adjustment of individual clip notes, e.g. to correct minor
recording mistakes, or to adjust timing, length or velocity of sequence notes:
Use the lower-left SELECT knob to choose the currently active note. A small dotted cursor
is drawn around it.
These operations are available on the top row of keys:
●Key 1 (Pos): horizontally adjust the note or correct its timing. Pushing the DATA
knb while turning will accelerate inputs, for instance to easily move a note longer
distances in the sequence.
●Key 2 (Note): adjust the note itself; here D#3 is shown, which could be adjusted to
any other MIDI note using the DATA knob.
●Key 3 (Vel): adjust the velocity of the note -- the individual note will be muted at
velocity value 0.
●Key 4 (Len): adjust the length of the played note relative to the recorded note
length.
●Key 6 (Delete): completely delete a note.
Tip: before undertaking extensive note editing, push COPY to store a copy of the clip
in the buffer. If editing goes wrong, press PASTE to undo.
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6.9 LIVEFX Screen
Use LiveFX functions to alter clips with effects designed for live performance:
These operations are selected with the top row of keys and modified with the VALUE knob
:
●Key 1 (QU) dynamically (re)quantizes clip notes to defined note lengths. In this
example a simple drum clip was requantized to 1/8th notes.
Tip: use requantization to alter the rhythmic structure of sequences. E.g. if the
above clip was requantized to 1/4th notes during playback, the audible speed
of the rhythm sequence would halve.
●Key 2 (SW) introduces swing to quantized clip notes. Swing is applied to every
second quantized note. A swing setting of 50% indicates that no swing is applied
and the note should stay at its quantized position. Swing values >50% (such as 66%
in the example above) push every second quantized note forward in time up to the
next quantization point, and swing values <50% push the note backwards in time.
Tip: 32/33% or 66/67% swing settings enable triplet swing timing
Tip #2: The swing effect sometimes changes dramatically with only slightly
altered BPM, try it out!
●Key 3 (PR) introduces non-zero note-skip probabilities. These are visualized as a
randomly blinking note-cloud. A note-skip probability of 100% would mute all
notes in the sequence.
Tip: A low note-skip probability of a few percent can spice up otherwise static
drumloops
Tip #2: Use note-skip probabilities in a live performance to "break up"/"fade
out" a sequence. It is especially fun to use on polyphonic/chord sequences! :)
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