right.

I understand that Modulation is a key to keeping any sounds interesting...but often the synth line repeats itself, even if it is being modulated. Maybe every 2bars, maybe every 4bars, etc.

Also, even if the drums/percussion change subtly within a track do they change so much that they never repeat themselves?

I hear ya on the dj tool tip. Some techno is just the first 4bars over and over and over. But I still think all music is based on loops, except maybe pure improv.