How much free time are you willing to devote (20 hours a week? 90?)? How many channels repeat things being done elsewhere?
For my 80-channel sequences, first pass on a two-minute song is usually about three or four hours. When I get brain freeze I walk away. I’ll come back a couple of days later and fiddle with it for another hour or so and it’s probably very close to being finished, though, they’re one of those things that you can tinker with and tinker with.
Three-minute, 20-second song, 4640 channels? Wild guess: 12 hours? 16 hours? Maybe even 24 hours?
I'm thinking you'll be happy with four songs rather than 15.
\dmc