SNES:Audio Information
Overview
The SNES/SFC uses a sample-based audio chip designed by Sony that functions similar to a ROMpler, in that the composer or sound designer loads in very small audio samples that are looped in oscillation similar to how a synthesizer oscillates a waveform. The oscillating sample is then pitched up and down as needed to create different notes by adjusting the playback speed--and thus the loop point--of the sample. This is the reason for the SNES/SFC's signature "stutter" sound that seems to speed up with higher notes and slow down with lower notes. Due to memory limitations, the samples must also fit within a very low bitrate, losing most of their high frequencies in the process. This is why the SNES/SFC's audio sounds so characteristically "warm" compared to its peers, or even outboard PC MIDI solutions like the Roland Sound Canvas, etc. All models of the SNES/SFC produce stereo audio, with a rudimentary DSP system via Sony's chipset that allows for very simple effects like reverb and delay, also in stereo.
Surround Sound
Every model of the SNES/SFC is also capable of matrixed multi-channel surround sound. This is achieved by piggybacking an inverted-phase signal across both left and right audio channels. Under normal stereo configuration circumstances, this results in standard stereo audio. But if the signal is sent to a device (such as a home theater receiver or dedicated outboard surround decoder) capable of decoding matrixed surround, a true multi-channel surround sound experience is achieved. There are the standard stereo left and right signals, but compatible games (notably Super Turrican, Jurassic Park, Fatal Fury Special to name a few) will be sending a limited-bandwidth inverted-phase signal across each of the two stereo RCA cables, that are decoded by the appropriate device into a Center and a Rear channel as well! This is how Dolby Surround works, and it's the same as the way it works on VHS and some LaserDiscs as well as some early DVDs and other 1990s game consoles. Some games paid for a Dolby license and had the Dolby Surround logo printed on the box or even the cartridge label, they were designed specifically to be decoded by Dolby Pro-Logic, which was the codec (for lack of a better word) for decoding Dolby Surround. Other games didn't pay for a Dolby license but still offered a Surround option in the audio options in-game that was decoded the same way. Still other games simply had "Mono" or "Stereo" options in the in-game menu, but the "Stereo" option was also passing along a matrixed surround signal and could be decoded appropriately. Final Fantasy VI is one such example. Due to the simple analog nature of the matrixed surround format being sent automatically across the two left and right audio channels, this means it also works with devices such as the MiSTer, Analogue SuperNT, and software emulators as well, provided the audio signal is being fed to a device that can look for and decode a Dolby Surround signal. Some modern AV Receivers are quietly dropping compatibility with older surround formats, but others are holding strong. It is recommended to research the surround format capabilities of a given receiver before purchasing new.