Composed by K. Jose on December 8, 2018
Audio characteristics based on SN76489 soundchip used in Sega systems
On pattern 11 row 84, I stopped the square tone at channel 3 and let the bass
line continue at channel 4 which is supposed to be for noise. Note
frequencies on the SN76489 are limited to note A2 at minimum for square
tones. The noise channel has 2 modes: white and periodic (which is a 6.25%
pulse wave). It has 3 predefined frequencies, which register on periodic
noise as A2, A3, or A4, or can follow the frequency of the 3rd square tone
channel. The 3rd channel is usually muted when the noise channel follows its
frequency. The same frequency setting input fed to the soundchip will produce
a note 4 octaves lower on periodic noise tone than on square tone.