WASM-4 audio too loud
WASM-4's audio is significantly louder than is reasonable. Here in the audio graph, you can see clips of a 440 Hz pulse wave tone in each mode. WASM-4 comes in at -6 dB, twice as loud as both Famitracker (an NES music tracker) and FCEUX (a popular NES emulator), both at -12 dB. I would take a guess that we'd find similar results with GameBoy emulators.

![image](https://user-images.githubusercontent.com/89336634/147188832-f7013b88-6d5b-4bc0-b613-91187dbd4220.png)

This is an issue especially for headphone users. Being twice as loud as the maximum volume of other retro systems, to my ears, is nigh on unbearable. I have to wonder if others feel the same way. This is exacerbated by the fact that there is no global volume control anywhere in WASM-4. The only alternative is changing the sustain volume, rendering the attack and decay controls effectively unusable (since they always peak at 100% volume).

To solve, I would recommend scaling the audio amplitude to one half of what it is currently, to bring this fantasy console in line with its retro contemporaries. We could also add a global volume, perhaps a signed byte which maps values [-128, 127] to volumes [0%, 100%].