@vic20owner
MIDI files are essentially a steams of event data. An event can be many things, but typically "note on", "note off", "program change", "controller change", type messages that instruct a MIDI compatible synth how to play a given bit of music. A midi file typically contains music that plays on up to 16 channels (as per the midi standard), but many notes can simultaneously play on each channel (depending on the limit of the midi hardware playing it).
Generally, MODs are similar in that they contain note on/off and other sequence messages that control the mod player. Unlike (most) midi files, however, they also contain sound samples that the sequence information actually plays. MOD files can have many channels (classic amiga mods have 4, corresponding to the inbuilt sound channels), but unlike MIDI, each channel can typically play only one note at once. However, since that note might be a sample of a chord, a drumloop or other complex sound, this is not particulalry limiting as it sounds.
There are a plethora of MOD formats that originated from different packages but they all have the above basic characteristics in common.
