Coins exist, and one amount is documented
Coins entered the game with the official 09/09/26 update ("earn in-game coins and buy custom mics"). No per-round payout, win bonus, or conversion rate has ever been published. The single documented amount anywhere in the economy is the THANKYOU code reward: 150 Coins.
The mic shop is the documented coin sink
Custom mics are the named things coins buy. Their catalog and prices are unpublished, so the ratio between how fast you earn and what mics cost cannot be computed from public data yet — that is a fact about the game's disclosure, not a gap in this site.
Codes are the documented top-up
The official description sends every player to the Buffboy Games group for codes. A new code is the one moment a player's balance moves by a publicly known amount, which is why code watch is an economy activity and not just a rewards activity.
The session arithmetic you can do today
Make That Sound! servers hold 8 players (official page), so a round cycle is bounded by real people taking turns. Measure your own loop tonight: rounds completed per 30 minutes, how the room's rating behaves, and your balance before and after. Those observations are the inputs a future calculator will need — and they are yours, not invented constants.