Multi-channel midi-capable audio/midi player on the Raspberry Pi platform using Python 3.
By D. Cooper Dalrymple, 2021
Octopy is intended to be used to play audio tracks synchronized with midi tracks when triggered by midi for the purpose of live music performances. This way, midi-controlled devices (drum machines, keyboards, etc) can be sequenced with a backing track and controlled by a simple and fitting midi device all within a small package, no laptops and fancy DAWs required.
This software could also be configured to play midi files into a midi sound device such as the MT32 or simply play back audio files for other purposes triggered from a device in another location. It is not required that both audio & midi files are provided for each track.
- Raspberry Pi 3 or greater - Raspberry Pi 1 experiences stuttering in midi and audio output (Model 3 A+ used for testing)
- Linux-based x86-64/ARM computer - This software has not been optimized for Windows or Mac
- HiFiBerry Audio Hats - Tested with the DAC+ Standard
- Serial-based MIDI Hats - ie: OSA MIDI Board (custom board used for testing)
- Linux-based OS - ideally Raspberry Pi OS Lite
- Python 3.x with pyalsaaudio, python-rtmidi, pyserial, wave, and mido modules
- ALSA
- JACK Audio Connection Kit
On Ubuntu/Debian/Raspbian systems, ensure that all dependencies are met by typing sudo apt-get install libasound2-dev libjack-dev and pip3 install pyalsaaudio python-rtmidi pyserial wave mido in the terminal.
A configuration file can be used for configuring the default settings for the program. All of the default settings are set by config.ini in the octopy directory. Copy this file to ~/octopy.ini to override its values.
If you'd like to automatically mount and search an external storage device such as a USB drive, install the pip packages and run octo.py with sudo. Then use the name of the device (such as "sda1") with the -m argument or configure Media -> Storage in the user config file. Only files in the top-level directory will be scanned when building the database.
Type python3 octo.py in the top level directory to run the program. Type python3 octo.py --help for command information. The command arguments will override any settings defined by the configuration files.
All discovered sound/midi files are listed in alphabetical order when you first run the program with the --verbose flag set. When a midi note is received on the selected channel (or on all channels by default) that corresponds with number value of the song, it will begin playing along the wave file and midi data depending on what is available (both, only midi, or only wave). If any files were playing previously, they are immediately stopped before the new file begins playing. If the a midi note is received with the note value of 0, it stops all currently playing streams.
This setup may not be ideal for use with a keyboard, but a properly configured midi pad device (such as the Akai LPD8) where each midi note is configured for the desired song and one of the pads is reserved as a stop pad should do the job. Organizing your files to begin with a number signifying the desired MIDI note (with a leading-zero ideally) will help with keeping everything in the proper order.
This software supports both USB midi devices or GPIO midi over the Raspberry Pi's serial interface. See this page for information about configuring the serial port on your Pi.
Any ALSA-enabled playback interface can be used. See the listed "Available Audio Devices" when you run the program with verbose enabled. A DAC hat such as the HiFiBerry DAC can also be used for audio playback (see for details).