I noticed a while ago that some music needs active listening[1], while other kinds[2] don't distract me.

1 - Rock, various kinds of progressive music, anything with nontrivial melody

2 - ambient, more monotonous music, music with uniform volume

I'd love to say I've started dividing my music collection according to this criteria - but I've been too lazy so far. Sorry about that. I'll try once again.