AlsaMidiOverview

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There's a huge difference between the ALSA MIDI implementation and most other operating systems. With ALSA it is no problem to interconnect different applications on the same computer.

Make sure that ALSA found your soundcard

cat /proc/asound/cards

There is a difference between hardware MIDI ports and software MIDI ports (virtual ports), but in practice every well-written ALSA app should work with both.

amidi -l

gives you a listing of the available hardware MIDI ports on your system. Here's the output on my machine:

tapas@mango:~$ amidi -l
Device    Name
hw:0,0    CS46XX
hw:1,0    Virtual Raw MIDI (16 subdevices)
hw:1,1    Virtual Raw MIDI (16 subdevices)
hw:1,2    Virtual Raw MIDI (16 subdevices)
hw:1,3    Virtual Raw MIDI (16 subdevices)

This output shows that I effectively have two soundcards. One of them is the virmidi module that provides 4 "virtual" hardware ports. These can be used to connect apps that insist on using hardware MIDI ports.

The command aconnect, which is also used to connect software MIDI ports, can give you a listing of all MIDI ports (both software and hardware MIDI ports):

tapas@mango:~$ aconnect  -i -o  
client 0: 'System' [type=kernel]
    0 'Timer           '
    1 'Announce        '
client 62: 'Midi Through' [type=kernel]
    0 'Midi Through Port-0'
client 64: 'Rawmidi 0 - CS46XX' [type=kernel]
    0 'CS46XX          '
client 72: 'Virtual Raw MIDI 1-0' [type=kernel]
    0 'VirMIDI 1-0     '
client 73: 'Virtual Raw MIDI 1-1' [type=kernel]
    0 'VirMIDI 1-1     '
client 74: 'Virtual Raw MIDI 1-2' [type=kernel]
    0 'VirMIDI 1-2     '
client 75: 'Virtual Raw MIDI 1-3' [type=kernel]
    0 'VirMIDI 1-3     '
client 129: 'FLUID Synth (11157)' [type=user]
    0 'Synth input port (11157)'
client 130: 'Virtual Keyboard' [type=user]
    0 'Virtual Keyboard'

The "-i" and "-o" options tell aconnect to list both writable and readable ports (input and output). See the output of the command "man aconnect" to get more info.

As we can see from above listing from aconnect, I have two programs running that provide software MIDI ports. This part of the listing is shown again below:

​1) fluidsynth:

client 129: 'FLUID Synth (11157)' [type=user]
    0 'Synth input port (11157)'

​2) vkeybd:

client 130: 'Virtual Keyboard' [type=user]
    0 'Virtual Keyboard'

FluidSynth is a software synthesizer that can load soundfonts. vkeybd is a virtual keyboard that can generate MIDI events. We will connect the two now.

tapas@mango:~$ aconnect 130:0 129:0

After this I can just play around with the keys on the vkeybd and fluidsynth plays the appropriate notes.

Of course, I can also connect vkeybd to a hardware MIDI port:

tapas@mango:~$ aconnect 130:0 64:0

Now, every key press goes to fluidsynth [we haven't disconnected it yet] AND to the hardware MIDI output port on my soundcard. That's one of the nice things about ALSA: you can connect a MIDI source to any number of MIDI destinations. And you can connect any number of MIDI sources to a MIDI destination. Very nifty.

Using aconnect can be tedious. That's why I usually use a graphical patchbay to connect MIDI stuff. See AlsaMidiPatchbays.

Retrieved from "http://alsa.opensrc.org/AlsaMidiOverview"

Category: MIDI

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