Music, binary output from server?

[Philipp Lenssen]

Is there any way to programmatically create e.g. MIDI output via parameters?
Could I include like the following on a webpage:
<bgsound="http://www.example.com/cgi-bin/midi.py?notes=cdfcdf" />

Well I'm sure there must be a way, but has this been done before, are there
open source libraries? (I'm not mainly concerned about MIDI, any music type
that works in popular browsers should be OK.)