only one MIDI at a time

i ve been reading about Java and Sound
this is what i get:32 channels for sampled audio 32 channels for MIDI
so i suppose that if you have a MIDI sequence with 7 instruments, 7 out of the 32 channels are being used (or one channel for each sequence? )

why cant i have another MIDI sequence playing ??? i have 25 remaining, unused ( or not ? ) channels

its kind of a theoritical question,so i suppose i will need a theoretical answer ( e.g. this was done by Sun engineers for reasons A,B and C)

thank you