Midimagic is envisioned to be a central entry point for digital controlling devices communicating via MIDI (e.g. MIDI keyboards, sequencers, DAWs and such) to a analog synthesizer setup.
This document explains the behaviour of Midimagic and how you can use it in your setup. A basic knowledge of the MIDI protocol and it's concepts is expected from the reader. See MIDI-Wikipedia
For a guide about the user interface see here.
Until today Midimagic supports the following message types:
- Note Off
- Note On
- Polyphonic Aftertouch
- Control Change
- Monophonic/Channel Aftertouch
- Pitch Bend
- MIDI Clock/Start/Continue
More System message types other than Clock might be added in the future.
See Ports for more information about the behaviour of ports when receiving messages.
Each portgroup operates on a single MIDI channel and distributes incoming messages via a demuxer to associated output ports. Portgroups can have overlapping sets of input types and output ports, for example:
Portgroup 1 listens for NoteOn and NoteOff messages and sends them to the ports 1 to 3.
Portgroup 2 listens for Pitch Bend messages and sends them to the ports 1 to 4.
Using this setup one would have 1V/octave pitch control voltage combined with the pitch bend shift on ports 1 to 3 and pitch bend CV only on port 4 for other uses.
More on the interpretation of different message types in the section Ports. See Examples for more possible use cases.
When setup to receive Control Change messages an additional property per Portgroup is used: One MIDI controller to listen to
A Demuxer distributes messages to ports following one of 3 available methods:
- Random
1 port is randomly picked
- Identic
Every message on all ports
- FIFO
The first free/inactive port is picked, if all ports are currently assigned/active the "oldest"/longest active one is chosen.
This is usefull for playing polyphonically with multiple oscillators for example.
Each port consists of a variable voltage and a gate/trigger output. The variable/control voltage (analog) output has a range of +/-5V and is used for continuous voltage such as pitch CV. The gate/trigger is a digital (low/high) output to indicate a change (trigger) of the continuous CV value output or gate representing a pressed key for example. Available voltages levels are either 0V or 10V. The 2 outputs are used diffently depending on the type of received message.
The different MIDI message types are interpreted as follows:
| Type | Hex value | Analog output | Digital output |
|---|---|---|---|
| Note On | 0x08 | The pitch information as halftone offset from C4 with 1V/Oct scaling Or note velocity | High voltage until Note Off for the note is received |
| Note Off | 0x09 | unchanged | Low voltage |
| Polyphonic Key Pressure/Aftertouch | 0xA | Raw value scaled to ~2.5V | unchanged |
| Control Change | 0xB | Raw value | Low if value is less than 64, else High (as per MIDI spec) |
| Program Change | 0xC | Ignored * | |
| Channel Pressure/Monophonic Aftertouch | 0xD | Raw value scaled to ~2.5V | unchanged |
| Pitch Bend | 0xE | Raw value scaled to 2 halftones (as per MIDI spec), but is added to the current value if port is active | unchanged |
| Clock | 0xF8 | unchanged | Rate adjustable trigger with 5 clock ticks duty cycle |
| Start | 0xFA | unchanged | Resyncs clock period on the next clock message |
| Continue | 0xFB | unchanged | idem |
*Program Change messages are supposed to control the MIDI receiver, Midimagic itself in this case. As there is no concept of how Midimagic is supposed to react to these types they are ignored for now. Do you have an idea or suggestion as to how to control Midimagic via Program changes? Let us know!
Here are a few suggestions of how to setup and work with Midimagic. Feel free to adapt and enhance these in your setup. All ports and MIDI channels noted are only exemplary and can be changed for your needs.
A simple monophonic setup
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| Note On |====>| Portgroup 1 | Demuxer =====>| Port 1 |
| Note Off | | Channel 1 | Identic | | Port 2 |
| | | ----------| | Port 3 |
| | | | | Port 4 |
---------------------------- ---------------------------- ---------------------------
A simple polyphonic setup to control 3 VCOs
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| Note On |====>| Portgroup 1 | Demuxer =====>| Port 1 |
| Note Off | | Channel 1 | FIFO | | Port 2 |
| | | ----------| | Port 3 |
| | | | | |
---------------------------- ---------------------------- ---------------------------
Combine Note messages from different MIDI channels to the same ports with Pitch Bend from channel 1
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| Note On |====>| Portgroup 1 | Demuxer =====>| Port 1 |
| Note Off | | Channel 1 | FIFO | | Port 2 |
| | | ----------| | Port 3 |
| | | | | |
---------------------------- ---------------------------- ---------------------------
---------------------------- ---------------------------- ---------------------------
| Note On |====>| Portgroup 2 | Demuxer =====>| Port 1 |
| Note Off | | Channel 5 | FIFO | | Port 2 |
| | | ----------| | Port 3 |
| | | | | |
---------------------------- ---------------------------- ---------------------------
---------------------------- ---------------------------- ---------------------------
| Pitch Bend |====>| Portgroup 3 | Demuxer =====>| Port 1 |
| | | Channel 1 | Identic | | Port 2 |
| | | ----------| | Port 3 |
| | | | | |
---------------------------- ---------------------------- ---------------------------
Use Pitch and Velocity CV in parallel
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| Note On |====>| Portgroup 1 | Demuxer =====>| Port 1 (in pitch mode) |
| Note Off | | Channel 3 | FIFO | | Port 2 (in pitch mode) |
| | | ----------| | Port 3 (in pitch mode) |
| | | | | |
---------------------------- ---------------------------- ---------------------------
---------------------------- ---------------------------- -----------------------------
| Note On |====>| Portgroup 2 | Demuxer =====>| Port 4 (in velocity mode) |
| Note Off | | Channel 3 | FIFO | | Port 5 (in velocity mode) |
| | | ----------| | Port 6 (in velocity mode) |
| | | | | |
---------------------------- ---------------------------- -----------------------------
Output Clock pulses and Monophonic Aftertouch parallel on the same port
Aftertouch will change the analog output while Clock will change only the digital output
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| Clock |====>| Portgroup 1 | Demuxer =====>| Port 8 |
| Channel Pressure | | Channel 1 | Identic | | |
| | | ----------| | |
| | | | | |
---------------------------- ---------------------------- ---------------------------
Use different Controllers simultaneously
As the purposes of MIDI Controllers are merely suggestions it is up to the user what is to be controlled by them. E.g. Controller 7 could be controlled via a MIDI clip from a DAW to adjust the cutoff frequency of a VCF.
---------------------------- ---------------------------- ---------------------------
| Control Change |====>| Portgroup 1 | Demuxer =====>| Port 5 |
| | | Channel 1 | Identic | | |
| | | ----------| | |
| | | Controller 1 (Mod wheel) | | |
---------------------------- ---------------------------- ---------------------------
---------------------------- ---------------------------- ---------------------------
| Control Change |====>| Portgroup 2 | Demuxer =====>| Port 6 |
| | | Channel 1 | Identic | | |
| | | ----------| | |
| | | Controller 7 (Volume) | | |
---------------------------- ---------------------------- ---------------------------
---------------------------- ---------------------------- ---------------------------
| Control Change |====>| Portgroup 3 | Demuxer =====>| Port 7 |
| | | Channel 1 | Identic | | |
| | | ----------| | |
| | | Controller 11(Expression)| | |
---------------------------- ---------------------------- ---------------------------
More experimental examples:
Distribute Notes randomly but have Pitch Bend on all ports
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| Note On |====>| Portgroup 1 | Demuxer =====>| Port 1 |
| Note Off | | Channel 1 | Random | | Port 2 |
| | | ----------| | Port 3 |
| | | | | |
---------------------------- ---------------------------- ---------------------------
---------------------------- ---------------------------- ---------------------------
| Pitch Bend |====>| Portgroup 2 | Demuxer =====>| Port 1 |
| | | Channel 1 | Identic | | Port 2 |
| | | ----------| | Port 3 |
| | | | | |
---------------------------- ---------------------------- ---------------------------
Pitch CV and Clock as ADSR trigger on the same port (clock retriggers the notes like an arppegiator)
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| Note On |====>| Portgroup 1 | Demuxer =====>| Port 5 |
| Note Off | | Channel 1 | Identic | | |
| Clock | | ----------| | |
| | | | | |
---------------------------- ---------------------------- ---------------------------
Use MIDI Clock as random triggers
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| Clock |====>| Portgroup 1 | Demuxer =====>| Port 5 |
| | | Channel 1 | Random | | Port 6 |
| | | ----------| | Port 7 |
| | | | | Port 8 |
---------------------------- ---------------------------- ---------------------------
As mentioned before any combination of message types or ports is possible.