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Looking for hardware recommendations for self-contained MIDI
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Looking for hardware recommendations for self-contained MIDI

by gregjohnellis on Sat May 08, 2021 2:07 pm

I'm just getting into this world and am finding it challenging what board(s) to select for a particular project.

I'd like to make a self-contained MIDI instrument (that both produces MIDI signals, and as a MIDI player to interpret and play the signals in realtime).

I'm thinking of using the Playground Express and it's cool touch capacitance feature to generate MIDI signals, but am unsure of a board that readily interprets them. Reading the description for the Music Maker Featherwing board, I see that it has a "Built in MIDI synth/drum machine with dozens of instruments". This seems to be the board! But, I have a few questions:

1. Is this really the board I'm looking for?
2. Is it polyphonic? (If I trigger MIDI sounds at the same time or close together, will they all play?)

Also, I am hoping to add some post-effects to the audio out signal. Are there any good boards or circuits for this (such as echo, delay and chorus)?

The installation will be a part of a sound sculpture that uses both acoustic, mechanically actuated percussive sounds (tube bells) as well as enhancing the instrument with MIDI out using the tube bells as touch capacitors to trigger MIDI.

gregjohnellis
 
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Re: Looking for hardware recommendations for self-contained

by blnkjns on Sun May 09, 2021 4:03 am

The board has 40 sustained channels of polyphony, but bear in mind that it is a single-chip General MIDI module. General MIDI can sound pretty cheesy.
https://www.youtube.com/watch?v=-h1pQKbXh8w
If you want a board to create your own polyphonic sounds, go to the boards that have a lively DIY synth making community, like the Teensy 3.2 or the Teensy 4 with DAC.
Teensy synth sample:
https://www.youtube.com/watch?v=nU_YfTbGYw0
The Teensy 4.1 has an SD slot, so you can feed it custom samples and wave-table files, not possible with the Music Maker Featherwing (only monophonic on SD playback).
You will need to deal with C++ coding, as polyphonic synthesizing is pretty demanding and needs low level processing. Good thing is there are tons of examples. The 4 is 600MHz and really powerful (like 5 Pi Pico's in one). It can do all the filtering and FX as well. Here are the Teensy boards:
https://www.adafruit.com/product/2756
https://www.adafruit.com/product/4323
https://www.adafruit.com/product/4622

If you just need to interface physcial controls with MIDI (sans sound generation), you can just start with the Feather 32U4 with Midi shield.
https://www.adafruit.com/product/4740
https://www.adafruit.com/product/2771
Or for enough power to generate sound:
https://www.adafruit.com/product/3857
The last board will probably run the Teensy synth sample code as well throught the built-in DAC. The M4 is 120-200MHz, the Teensy 3.2 is 72MHz, so you have some overhead.
Capacitive input can be added to any board, I would not put that as key spec when selecting a board.

For understanding MIDI (it is REALLY simple), it is good to start with the MIDI featherwing and just load the Serial Passthrough sketch from Arduino samples and start hitting keys on another MIDI keyboard. You will see the incoming data and it is easy to understand. From there start sending out similar commands to the MIDI-out. If you have the hang of it, it is easier to adjust a piece of synth code to interact with MIDI the way you like.

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Re: Looking for hardware recommendations for self-contained

by gregjohnellis on Wed May 19, 2021 9:21 pm

Thanks so much, this is an extremely helpful reply!!

gregjohnellis
 
Posts: 4
Joined: Sat May 08, 2021 1:50 pm

Please be positive and constructive with your questions and comments.