As you have observed, there is no description of the API.
Linux didn't have one either when I last looked.  You can
look at the source for midiplay(1), and get some hints.

    -- Lennart


der Mouse wrote:

>I want to start playing with MIDI.  I have a soundcard which apparently
>has not only a physical MIDI port but also a synth on it:
>
>sb0 at isa0 port 0x220-0x237 irq 5 drq 1 drq2 5: dsp v4.12
>audio0 at sb0: full duplex, mmap, independent
>midi0 at sb0: SB MIDI UART
>opl0 at sb0: model OPL3
>midi1 at opl0: SB Yamaha OPL3
>
>However, I can't find any description of any relevant APIs.  The
>closest I find is in midi(4), which says
>
>     The API for the sequencer device is binary compatible with the OSS se-
>     quencer interface.
>
>However, it fails to describe "the OSS sequencer interface".  It does
>have a SEE ALSO for ossaudio(3), but that is singularly unhelpful:
>
>DESCRIPTION
>     The ossaudio library provides an emulation of the OSS (Linux) audio in-
>     terface.
>
>     Use the native interface for new programs and the emulation library only
>     for porting programs.
>
>What is "the native interface"?  I have no clue, nor any idea where to
>find one...short of asking here. :-)
>
>Any pointers would be most welcomed.
>
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