SMF is Standard MIDI File and the difference has nothing to do with Wheteher the file contains GM deisgnators or not.

All MIDI files are SMF these days.

GM simply means that the 16 channels are assigned according to the General MIDI bank.

For drums, that means that the Percussion Channel will always be MIDI channel 10.

On a few older synths, it might be MIDI channel 16.

If you hear, like a Grand Piano pounding away the drum line on a MIDI synth, check that Percussion channel assignment for that's what is wrong.


--Mac