Despite having known of In C for years (thanks, Music History 101), it was only recently that I listened to an actual performance of it!
Many consider In C to be the first piece of minimalist music. It consists of 53 numbered bits of music with the instructions to play each one however many times you choose. The players in the group are instructed to stay within 2-3 phrases of each other, and there’s also a pianist or mallet percussionist playing a steady pulse on the note C for the duration. It can be played by ensembles of any size and instrumentation, which is why it’ll work nicely for this fictional hodgepodge of a start-up ensemble.