You have heard the primes modulo seven, and hopefully you noted that
all seven notes were played but that the lowest note occurred just once.
The lowest note was the fourth note played and came from the prime seven,
which, of course, leaves a remainder of zero. (Any number that leaves a
remainder of zero when divide by seven is a multiple of seven--so can only
be prime if it is exactly seven.) By Dirichlet'’s theorem on primes
in arithmetic progressions (a mouthful eh?), all of the other notes
are played infinitely often as we play all of the primes.

Now listen to the primes modulo six (on a percussion organ) as we again pause for a question
break.

If you prefer, here are the same primes (the first 300) played with percussion only.