I don't mean to pick on the author... but there are some common LLM-isms in here which are really starting to annoy me:

    return (int64_t)(now_us - deadline_us) >= 0;

...is a very silly way of saying:

    return now_us >= deadline_us;

The function is named incorrectly, "deadline passed" would be:

    return now_us > deadline_us;

...although the calling function is correctly called "wait until", making it more confusing if you had to care about the difference.

The weirdly pedantic use of stdint.h types with unnecessary casting is another LLM-ism I see more and more. Passing int8_t to a function by value is really weird... and the second half of this conditional:

    if (midi_note < 0 || midi_note > 127) {

...can never be true, INT8_MAX is 127.

None of this is a huge problem on it's own. But the cognitive cost of a million odd little things like this adds up really quickly across a large codebase when you're trying to debug something.