MIDI externals

[Ken Norris]

Howdy,

Is there an external for Windows (I think they're called DLL's?) that 
will select instruments and play MIDI notes instantly? Not necessarily 
a song sequence, but a note or chord.

It's for an onscreen keyboard, i.e., must play the note instantaneously 
on mouseDown. Actually, I'm looking for it to play like a piano, when 
the user drags over the 'keys', but that's more a scripting issue. I 
have one working in SuperCard on the Mac, using QuickNotes. I wouldn't 
mind building a cross-platfrom version, but it has to perform as I 
indicated.

TIA,
Ken N.