Let's see... Couldn't we just do away with the concept of N+ and N- development times and simply develop at the same time to different music?
Need an expansion, put on the William Tell Overture, "Hi-ho Silver! Away!" Need a contraction, how about the adagio from Mahler's ninth. Normal? a Mozart allegro? Would the negatives look cooler if I listened to Miles Davis instead of Mozart? Maybe heroic classical music for landscapes, jazz or rock for gritty cityscapes, soft harp music for still-lifes? The possibilities are endless...
Maybe I'll stick to my kitchen timer though.