A Julia MIDI Mixer / Player with an OpenGL based GUI



Mplay is a full functional MIDI player written in pure Julia. It reads Standard MIDI Files (SMF) and sends them to MIDI devices (or software synthesizers) while giving visual feedback.

This is a pre-release which runs on macOS X and Windows. Mplay has been tested with Julia 1.0 (or later) and GLFW 1.5.

macOS X and Windows systems come with a builtin software synthesizer (Apple DLS SoftSynth, Microsoft GS Wavetable SW Synth). On those systems Mplay runs out of the box. However, best results can be achieved with the Roland Sound Canvas VA software synthesizer:



  • Full functional MIDI player
  • Mixer with mute and solo options
  • Ability to change channel parameters (delay, chorus, reverb, pan)
  • Volume sliders
  • Pulldown menus for GM instrument sounds
  • MIDI VU meter
  • Show note, chord and lyrics information
  • Change key, tempo
  • Transport controls
  • Keyboard shortcuts
Key Action
a un-mute all channels
b/B toggle/solo bass
d/D toggle/solo drums
g/G toggle/solo guitar(s)
k/K toggle/solo keyboard(s)
1234567890!@#$%^ toggle channel 1-16
-/+ decrease/increase tempo
SPACE stop/resume song
> < transpose up/down
TAB select next channel
ESC quit Mplay



On macOS X and Windows systems Mplay comes as a self-contained package with its own wrappers for GLFW and OpenGL as well as the required run-time libraries for the GUI and Midi subsystems.


using Mplay
mplay(<path to midi file>)

You can also create your own wrapper script to use Mplay from the command line (main.jl is contained in the package), e.g.:

julia main.jl <path to midi file>


Mplay has no innovative features - the main focus is on simplicity and ease of use. It uses texture blitting to guarantee highest refresh rates. That's why it responds in real-time in the order of milliseconds, both to user interactions and MIDI events.

If, for any reason, the contained MIDI run-time doesn't work, you can build your own binaries:

macOS X

cc -shared -o libmidi.dylib libmidi.c \
   -framework CoreMIDI -framework CoreAudio -framework AudioUnit \
   -framework AudioToolbox -framework Cocoa


cl /c libmidi.c
link /out:libmidi.dll libmidi.obj -dll winmm.lib

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