-Super Mario Land 2 - Pops in menu are fixed by immediately updating APU output after a write
-Perfect Dark - Low voice volume is fixed by having the correct output when the channels are disabled (but DAC is still enabled)
-Daiku no Gen - Low voice volume is fixed by keeping square channel output to digital 0 (= analog 1) until its first tick after being enabled (the game does not let the channel tick at all while the voice sample is playing)
Wave channel was playing the wrong audio on the title screen, because some writes were being blocked.
It looks like the restriction on wave "ram" access that exists on GB don't exist on GBA
Additionally, it seems like the wave data is supposed to be stored in a large shift register (not emulated yet), rather than an array of bytes
