Directmusic problems!

Hi, Just taking my first steps into the wonderfull world of directmusic. Got a problem already: I want to make an app, that can produce different notes with different instruments(kinda like a music-keyboard). I can produce the different notes, but I can''t choose a different instrument. This is what happens: I create everything, I load a segment file "sample.sgt" (from dx8SDK, I don''t need this because I gonna produce my own notes, but directmusic needs one anyhow) and I load a collection file "gm.dls"(standard directx collection). So now when I play the notes , I can hear a piano playing, but when I try to set a different instrument with "SendPatchPMSG" and I play, I hear nothing, Why??? Does anyone has a clue what I''m doing wrong? I would be very happy if someone could to help me.;-) Thanks, RiBa