cometsong by Desire [web]
Cometsong - 3-channel Mockingboard music with Lo-res graphics 256-byte Intro for Apple II, Lovebyte 2022 by Deater / dSr Fitting Mockingboard music in 256B was a challenge. Note: only plays music out the left stereo channel. Thanks to mA2E for the music. Thanks to qkumba for optimization help. This code does a lot of tricky things. It loads into the zero page (which makes memory use less) but the music data overflows into the low half of the stack (at $100 on 6502). The rest of the code avoids the use of the stack, so we can use the "PLA" (pull stack to accumulator) instruction to do an auto-increment load through the music. This trick saved 15+ bytes.
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