Second hint for the puzzle in CONF: the high-pitched piano has nothing to do with anything. The second piano is only playing major triads on a loop. The third piano playing the message is adding another note to the triad.
Edit to clarify
Third hint for the puzzle in CONF: The third piano playing the message is only playing either D, F#, or A and only one note at a time
Fourth hint for the puzzle in CONF: The A note in the message is a delimiter separating strings of D and F# notes and also padding at the end
Fifth hint for the puzzle in CONF: It's a code that has existed for at least 150 years, just using notes instead of symbols
May 24, 2024, 6:14 AM@trebach Try as I might, I can't hear the third piano which carries the code. Don't know if it's a levels thing, or a stereo separation thing (mono hearing here) or if I'm discounting a note I can hear as being part of the first or second piano.