sbright33:
How many tracks? That's easy. Sample them all at once. Either a simple envelope follower circuit for each track or do it in software. Don't let anyone tell you the Uno doesn't have enough processing power. Your project sounds simple compared to FFT. First some simple calculations. Let's say N tracks. 60khz/N = how often you can sample each track. If N=60 then only 1khz, which will miss the high end, but over time it doesn't matter. How often do you want to calculate a sound level?
Thanks for your help! 6 tracks, so 10kHz. Software or hardware, I don't know how to do it either way. Do you know where I can learn, starting from almost 0?