Low level, collect data and dispatch to handlers
- Francois Best MIDI Library (version 5 on GitHub but 4 may be simpler to use here)
- Paul Stoffregen USB MIDI Host using USBHost_t36
- Teensyduino USB MIDI
Note that Arduino USBMIDI claims to support Teensy 4.1 but does not support USB Host.
Note bug in MIDI.hpp re system common messages
Detect devices connected to USB host:
myusb.task() is what polls for a connected USB device.
High level, implement MIDI 1.0, HRV and and MPE specifications
- My own library.
Doesn't yet exist as a library but verious sketches implement parts.
Voice allocation is not in that library, module specific.
Range of musical frequencies for MIDI notes assuming :
- Equal temperament tuning
- MIDI 60 is C4, middle C (thus MIDI 69 is A4, concert A)
- A4 is 440Hz
- C4 is by default 0V, Doepfer Eurorack standard (thus tuning to 440Hz needs 0.75V)
- pitch CV range +5V to -5V
- DAC verification should avoid the note extremes to minimize linearity error
- With pitchbend, note numbers are non-integer
Voltage = 0.75 + (n - 69)/12
| MIDI | Name | Voltage | Frequency |
|---|---|---|---|
| 127 | G9 | 12,543.85 | |
| 120 | C9 | 5V | 8372.02 |
| 119 | B8 | 4 11/12V | 7902.13 |
| 117 | A8 | 4.75V | 7040.00 |
| 108 | C8 | 4V | 4186.01 |
| 105 | A7 | 3.75V | 3520.00 |
| 93 | A6 | 2.75V | 1760.00 |
| 81 | A5 | 1.75V | 880.00 |
| 69 | A4 | 0.75V | 440.00 |
| 60 | C4 | 0V | 261.63 |
| 57 | A3 | -0.25V | 220.00 |
| 45 | A2 | -1.25V | 110.00 |
| 36 | C2 | -2V | 65.41 |
| 33 | A1 | -2.25V | 55.00 |
| 24 | C1 | -3V | 32.70 |
| 21 | A0 | -3.25V | 27.50 |
| 16 | E0 | 20.60 | |
| 9 | A-1 | -4.25V | 16.35 |
| 0 | C-2 | -5V | 8.18 |
Frequencies for the A notes are exact, others are rounded. MIDI notes outside 88-key piano range are in italics.
Note that:
- A8 is a convenient 4.750 V corresponding to an exact integer frequency 7040 Hz
- C8 is a convenient 4v for testing, and also corresponds to the highest note on an 88-key piano
- C2 is -2V and also the lowest note on an 88-key piano
- A2 is a convenient -2.250 V corresponding to an exact integer frequency 55 Hz
- E0 is the lower limit of audibility
- A-1 is -4.25V and exact 16.350 Hz, useful for auto tuning
- MIDI notes 121 to 127 are unreachable with a ±5V DAC swing if the C4 = 0V Doepfer tuning is maintained. Also not musically useful notes.
- MIDI notes 0 to 15 inaudible, so not musically useful
Dispatching key events to the two channels: first one is lowest note priority, second channel is highest note priority. So can be used as one of two popular monosynth styles, as well as duophonic.
DIN MIDI is 31,250 baud with 10 bits (1 start, 8 data, 1 stop, no parity) per byte transferred = 3,125 bytes/sec. 3 bytes per MIDI CC means max update rate (for a single CC using all the bandwidth) is ~1000 CC per second.
Interesting quote from Haken MPE+:
Data smoothing is not a bad thing for the synthesizer to do — in fact, the Sampling Theorem tells us that smoothing is always necessary to avoid aliasing! Aliasing is not a problem unique to audio sample streams, but also X,Y,Z control streams encoded in Midi. The common sample rates for audio are 44.1, 48, or 96 kHz. The effective sample rate for the most popular MPE controllers’ Z data is ~25 Hz, and ~500 Hz for the Continuum Fingerboard. MPE+ lets the controller specify the best amount of smoothing to avoid update noise (aka zipper noise or aliasing) but still retain the finger motion information in the data. [Clarification: The Continuum internally has an effective sample rate of ~3 kHz for Z; this data is processed to create the optimized ~500 Hz effective sample rate control stream for Midi transmission.]
and, from the Sound on Sound review of the Expressive-E Osmose:
The Osmose’s internal control scheme is not based on MPE MIDI but an extension of it termed MPE+ that improves resolution in the domains of time (for very quick response) and magnitude (for very smooth). Interestingly, it does away with the concept of key velocity (or, in MPE terms, Strike Value) completely, and instead derives note onset information from ‘attack trajectory’, a much more precise assessment of key travel over time that can take into account key dip as well as rate and acceleration.
However, the Osmose will function perfectly well as an MPE or basic MIDI controller. It does that by deriving velocity data (or MPE Strike Value) from the initial key touch, and various types of channel or polyphonic pressure from the aftertouch. An ‘Ext MIDI’ mode, with a dedicated button, toggles the Osmose’s interface entirely over to MIDI control functions. And then a handful of dedicated MIDI control profiles are provided, including a full MPE implementation, ‘classic keyboard’ (which turns off all expressive features except velocity and channel aftertouch), and ‘poly aftertouch’ (which gives good compatibility with synths like the Oberheim OB‑6 that offer this response, but not full MPE). The point in the key dip at which notes trigger varies between modes: higher/earlier for MPE, and lower/later for ‘classic keyboard’. That’s some real sophistication, and very nicely considered.
See also the section 14-bit Controllers are Flawed and Control Voltage Converter (CVC) for Analog Synthesizers which has W,X,Y,Z outputs on four channels (using I2C, oddly), and similar Evaton Technologies µCVC.
Useful discussion on Osmose, CC87, CC74 for 14-bit output
MIDI BigBuffer to avoid losing data with high throughput
class MIDIDevice_BigBuffer required for 480 speed.
There are countless other such examples of historical and contemporary musical instrument intonation systems that would be able to easily illustrate the glaring shortcomings of being restricted to only 12 notes repeating at the 2/1. For musicians and composers to be able to encompass the full range of expression and compositional possibilities of using alternative intonation systems in their music – including, but not limited to, 12 Note Octave Repeating Microtunings – it is advised to support those visionary developers who have implemented full-keyboard microtuning in their instruments. With correctly implemented full-keyboard microtuning functionality, there is no compromise in the way that one may microtune their hardware or virtual instruments.
Virtual instruments that can more easily achieve high-precision full-controller microtuning are those where developers have implemented the use of either the TUN or MTS (MIDI Tuning Standard) microtuning formats, which enable saving all of the microtuning mapping information into a single tuning data file that may be loaded directly into the instruments, or in the case of MTS, also be transmitted from the timeline of DAWs that allow transmitting SYSEX, such as for example REAPER and Bitwig.
- How to create a .tun file in Scala also describes mts
- MIDI tuning frequency data format
TUN (.tun) is textual, one line for each of the 128 notes, while MTS (.mid) is binary, 3 bytes per note.
- Mapping microtonal scales to a MIDI keyboard in Scala
- re-tuned - same melodies in different tunings
- scale workshop browser-based scale generator
- Intro to Microtonality
- My Idiosyncratic Reasons for Using Just Intonation
- Book The Arithmetic of Listening
The SoS review of the Arturia Polybrute 12 mentions Pluck (short AD) and Touch (key position modified by ADSR) to control filter and VCA.
The third mode is FullTouch Env > AT, and this is the one that’s going to cause confusion, not least because the manual doesn’t describe it fully. (A lack of detail was a fault with the original PolyBrute manual, too.) Having spent hours trying to work out what was happening, I admitted defeat and contacted Arturia. It turns out that, when designing sounds to take advantage of FullTouch AT and FullTouch AT > Z, the developers found that they were leaving the filter and amplifier open so that they could use FullTouch to control other aspects of note development, timbre and modulation. So they designed a mode in which the VCF and VCA envelopes no longer act as ADSR contour generators, but are replaced by modulation values that are determined by the key velocity and vertical position. Having decided upon the basis of the system, they then decided to make each of those values the sum of two new signals. The first of these is called Pluck, and this is a simple AD transient. Its fastest attack rate is quoted as below 4ms, but it can be lengthened a little by increasing the value of the attack fader of the appropriate envelope generator. The decay rate is then controlled by the decay fader, and the maximum amplitude of the transient is controlled by the velocity fader, although there’s a lower velocity threshold that helps to ensure that you don’t generate a Pluck by accident. The second signal is called Touch, which is a contour determined by the position of the key at any given moment. However, the ADSR faders in each of the VCF and VCA envelope panes also affect this. The attack and decay faders determine the slew rate when the key moves down or up, respectively. The Sustain value is more complex. When positioned below 50 percent, the generated values are lower than they would otherwise be, lowering the relative amplitude of the Touch and emphasising the Pluck to create, well, plucked sounds. But when the Sustain is positioned above 50 percent, the Touch signal remains high. This was implemented so that the VCA can be kept open even while a key is being moved up and down to control the filter. The release fader then controls the release time as you would expect. Finally, the aftertouch sensor at the bottom of the key’s travel is again active, so you can still lean into a note and generate Poly‑AT in addition to all of the above.
Setup:
#include <USBHost_t36.h>
#include <MIDI.h>
USBHost thisUSB;
USBHub hub1(thisUSB);
MIDIDevice_BigBuffer usbhostMIDI(thisUSB);
MIDI_CREATE_DEFAULT_INSTANCE();
And then in the loop:
MIDI.read();
usbMIDI.read();
thisUSB.Task();
usbhostMIDI.read();
The USB host port has a TDP3S014 current limit chip. So the maximum current is either the limit this chip imposes (~850mA), or the remaining amount of current available from whatever power source is powering Teensy 4.1.
PaulStoffregen
This also provides D+ D- ESD protection.
The three sliders are by default (in MPE mode) set to CC 107, 109, 111 while the touchpad is set to x-axis CC 113, y-axis CC 114. However they seem to generate SysEx F0 instead.
TIMESTAMP IN PORT STATUS DATA1 DATA2 CHAN NOTE EVENT
Opened MIDI Input
Closed MIDI Input
Opened MIDI Input
00000BE7 2 -- F0 Buffer: 9 Bytes System Exclusive
SYSX: F0 00 21 10 78 3D 17 06 F7
00000C0F 2 -- F0 Buffer: 9 Bytes System Exclusive
SYSX: F0 00 21 10 78 3D 17 0A F7
00000C37 2 -- F0 Buffer: 9 Bytes System Exclusive
SYSX: F0 00 21 10 78 3D 17 1C F7
00000C60 2 -- F0 Buffer: 9 Bytes System Exclusive
SYSX: F0 00 21 10 78 3D 17 27 F7
And for keys (remembering in MPE 74 Brightness is used for front-back Slide)
TIMESTAMP IN PORT STATUS DATA1 DATA2 CHAN NOTE EVENT
Opened MIDI Input
0005534E 2 -- B1 4A 08 2 --- CC: Brightness
0005534E 2 -- E1 00 40 2 --- Pitch Bend
0005534E 2 -- 91 39 1E 2 A 3 Note On
00055358 2 -- B1 4A 06 2 --- CC: Brightness
0005535B 2 -- E1 00 40 2 --- Pitch Bend
00055362 2 -- D1 37 -- 2 --- Channel Aft
00055369 2 -- D1 39 -- 2 --- Channel Aft
00055370 2 -- D1 3B -- 2 --- Channel Aft
00055377 2 -- D1 3D -- 2 --- Channel Aft
0005537E 2 -- D1 3F -- 2 --- Channel Aft
00055384 2 -- D1 41 -- 2 --- Channel Aft
0005538B 2 -- D1 43 -- 2 --- Channel Aft
0005538B 2 -- B1 4A 05 2 --- CC: Brightness
00055392 2 -- D1 45 -- 2 --- Channel Aft
00055399 2 -- D1 47 -- 2 --- Channel Aft
000553A0 2 -- D1 49 -- 2 --- Channel Aft
000553A5 2 -- B1 4A 04 2 --- CC: Brightness
000553A7 2 -- D1 4B -- 2 --- Channel Aft
000553AE 2 -- D1 4D -- 2 --- Channel Aft
000553B5 2 -- D1 4F -- 2 --- Channel Aft
000553BC 2 -- D1 51 -- 2 --- Channel Aft
000553C3 2 -- D1 53 -- 2 --- Channel Aft
000553CA 2 -- D1 55 -- 2 --- Channel Aft
000553D1 2 -- D1 57 -- 2 --- Channel Aft
000553D8 2 -- D1 59 -- 2 --- Channel Aft
000553DF 2 -- D1 5B -- 2 --- Channel Aft
000553E7 2 -- D1 5D -- 2 --- Channel Aft
000553ED 2 -- D1 5F -- 2 --- Channel Aft
000553F3 2 -- B1 4A 05 2 --- CC: Brightness
000553FB 2 -- D1 60 -- 2 --- Channel Aft
00055409 2 -- D1 61 -- 2 --- Channel Aft
00055418 2 -- D1 62 -- 2 --- Channel Aft
0005541B 2 -- B1 4A 06 2 --- CC: Brightness
000554B8 2 -- D1 61 -- 2 --- Channel Aft
000554BF 2 -- D1 60 -- 2 --- Channel Aft
000554C6 2 -- D1 5E -- 2 --- Channel Aft
000554CD 2 -- D1 5D -- 2 --- Channel Aft
000554D3 2 -- E1 10 40 2 --- Pitch Bend
000554D4 2 -- D1 5F -- 2 --- Channel Aft
000554DC 2 -- D1 61 -- 2 --- Channel Aft
000554DE 2 -- B1 4A 07 2 --- CC: Brightness
000554E1 2 -- E1 24 40 2 --- Pitch Bend
000554E3 2 -- D1 63 -- 2 --- Channel Aft
000554EA 2 -- B1 4A 05 2 --- CC: Brightness
000554EE 2 -- E1 41 40 2 --- Pitch Bend
000554F1 2 -- D1 61 -- 2 --- Channel Aft
000554FB 2 -- E1 51 40 2 --- Pitch Bend
000554FF 2 -- D1 5F -- 2 --- Channel Aft
00055505 2 -- D1 5D -- 2 --- Channel Aft
00055507 2 -- E1 0E 41 2 --- Pitch Bend
0005550C 2 -- D1 5F -- 2 --- Channel Aft
00055512 2 -- B1 4A 04 2 --- CC: Brightness
00055514 2 -- D1 61 -- 2 --- Channel Aft
00055515 2 -- E1 1D 41 2 --- Pitch Bend
0005551B 2 -- D1 63 -- 2 --- Channel Aft
00055522 2 -- D1 65 -- 2 --- Channel Aft
00055522 2 -- E1 2A 41 2 --- Pitch Bend
00055529 2 -- D1 66 -- 2 --- Channel Aft
0005552C 2 -- B1 4A 06 2 --- CC: Brightness
0005552F 2 -- E1 39 41 2 --- Pitch Bend
00055530 2 -- D1 64 -- 2 --- Channel Aft
00055537 2 -- D1 62 -- 2 --- Channel Aft
0005553B 2 -- E1 7D 41 2 --- Pitch Bend
0005553D 2 -- D1 60 -- 2 --- Channel Aft
00055544 2 -- D1 62 -- 2 --- Channel Aft
00055545 2 -- B1 4A 03 2 --- CC: Brightness
00055548 2 -- E1 4D 42 2 --- Pitch Bend
0005554B 2 -- D1 64 -- 2 --- Channel Aft
00055552 2 -- D1 66 -- 2 --- Channel Aft
00055555 2 -- E1 54 42 2 --- Pitch Bend
00055559 2 -- D1 68 -- 2 --- Channel Aft
0005555F 2 -- B1 4A 04 2 --- CC: Brightness
00055560 2 -- D1 66 -- 2 --- Channel Aft
00055562 2 -- E1 6C 42 2 --- Pitch Bend
00055567 2 -- D1 68 -- 2 --- Channel Aft
0005556D 2 -- B1 4A 05 2 --- CC: Brightness
0005556F 2 -- D1 66 -- 2 --- Channel Aft
00055570 2 -- E1 0C 43 2 --- Pitch Bend
00055576 2 -- D1 64 -- 2 --- Channel Aft
00055579 2 -- B1 4A 04 2 --- CC: Brightness
0005557C 2 -- D1 66 -- 2 --- Channel Aft
0005557C 2 -- E1 26 43 2 --- Pitch Bend
00055583 2 -- D1 68 -- 2 --- Channel Aft
00055589 2 -- E1 2C 43 2 --- Pitch Bend
0005558A 2 -- D1 66 -- 2 --- Channel Aft
00055591 2 -- D1 64 -- 2 --- Channel Aft
00055593 2 -- B1 4A 08 2 --- CC: Brightness
00055596 2 -- E1 51 43 2 --- Pitch Bend
00055598 2 -- D1 62 -- 2 --- Channel Aft
000555A0 2 -- D1 64 -- 2 --- Channel Aft
000555A0 2 -- B1 4A 07 2 --- CC: Brightness
000555A3 2 -- E1 71 43 2 --- Pitch Bend
000555A6 2 -- D1 63 -- 2 --- Channel Aft
000555AD 2 -- D1 65 -- 2 --- Channel Aft
000555AE 2 -- B1 4A 06 2 --- CC: Brightness
000555B0 2 -- E1 7C 43 2 --- Pitch Bend
000555B4 2 -- D1 67 -- 2 --- Channel Aft
000555BB 2 -- B1 4A 07 2 --- CC: Brightness
000555BB 2 -- D1 69 -- 2 --- Channel Aft
000555BD 2 -- E1 00 44 2 --- Pitch Bend
000555C2 2 -- D1 6B -- 2 --- Channel Aft
000555C7 2 -- B1 4A 08 2 --- CC: Brightness
000555CA 2 -- D1 6D -- 2 --- Channel Aft
000555D0 2 -- D1 6F -- 2 --- Channel Aft
000555D7 2 -- D1 71 -- 2 --- Channel Aft
000555DF 2 -- D1 73 -- 2 --- Channel Aft
000555E6 2 -- D1 74 -- 2 --- Channel Aft
000555ED 2 -- D1 73 -- 2 --- Channel Aft
000555EF 2 -- B1 4A 09 2 --- CC: Brightness
00055602 2 -- D1 72 -- 2 --- Channel Aft
00055616 2 -- B1 4A 08 2 --- CC: Brightness
0005562C 2 -- D1 71 -- 2 --- Channel Aft
00055647 2 -- D1 70 -- 2 --- Channel Aft
0005565C 2 -- D1 6F -- 2 --- Channel Aft
00055663 2 -- D1 6E -- 2 --- Channel Aft
0005566A 2 -- D1 6D -- 2 --- Channel Aft
00055671 2 -- D1 6B -- 2 --- Channel Aft
00055678 2 -- D1 69 -- 2 --- Channel Aft
0005567D 2 -- B1 4A 07 2 --- CC: Brightness
0005567F 2 -- D1 67 -- 2 --- Channel Aft
00055686 2 -- D1 65 -- 2 --- Channel Aft
0005568D 2 -- D1 63 -- 2 --- Channel Aft
00055694 2 -- D1 61 -- 2 --- Channel Aft
00055697 2 -- B1 4A 08 2 --- CC: Brightness
0005569B 2 -- D1 5F -- 2 --- Channel Aft
000556A2 2 -- D1 5D -- 2 --- Channel Aft
000556A9 2 -- D1 5B -- 2 --- Channel Aft
000556B0 2 -- D1 59 -- 2 --- Channel Aft
000556B7 2 -- D1 57 -- 2 --- Channel Aft
000556BE 2 -- D1 55 -- 2 --- Channel Aft
000556C5 2 -- D1 53 -- 2 --- Channel Aft
000556CC 2 -- D1 51 -- 2 --- Channel Aft
000556D4 2 -- D1 4F -- 2 --- Channel Aft
000556D6 2 -- 81 39 39 2 A 3 Note Off
0005DB72 2 -- F0 Buffer: 9 Bytes System Exclusive
SYSX: F0 00 21 10 78 3E 28 06 F7
The short SysEx seems to be sent periodically as a sort of keep-alive? 00H 21H 10H is registered to ROLI Ltd. Presumably 78 is the device ID and 3E is the Seaboard Rise 1 Model ID? Although the earlier trace had 3D. Thus, 28 06 is the actual data.
I should also mention that, in addition to all of the above, the PolyBrute 12 supports MPE. When sending, all of the aftertouch modes send channel pressure on a per‑note basis, with the FullTouch Env > Z and FullTouch Env > AT modes sending MIDI CC74 as the secondary parameter when a key is pushed into the aftertouch sensor at the bottom of its travel. When receiving, channel aftertouch, poly aftertouch, FullTouch AT and FullTouch AT > Z are each routed to aftertouch and MIDI CC74 on a per‑note basis, while FullTouch Env > AT is routed to the VCF envelope and aftertouch respectively.