o hey,i should've had also tell you this earlier,but i kinda just updated the sb D:I'll add them to the tags!
iidx 13th's main theme is Custom Drive
iidx 12th's ending theme is CaptivAte ~Clean~
iidx 15th's main theme is THE FANG (TROOPERS STANCE)
they're all by dj yoshitaka ofcourse