in my (limited) experience playing my brother's pretty bad 12 string, they sounds best when just playing chords. They add a kind of jingle jangle thing to the sound and make the chords sound fuller, because there are twice as many notes. The strings are an octave apart except for on the high b and e strings, i think. Maybe if you play one enough, it'll sounds good doing solos and stuff, but I personally think they shine with chord progressions, acting as a backup to either another guitar or a singer.