• 3-channel synthesizer with programmable ADSR envelope
• 8 octaves
• 4 waveforms: triangle, sawtooth, variable pulse, noise
• Oscillator synchronization, ring modulation
• Programmable filter: high pass, low pass, band pass, notch filter

The sound chip, SID, had three channels, each with its own ADSR envelope generator, and with several different waveforms, ring modulation and filter capabilities. It too, was very advanced for its time. It was designed by Bob Yannes, who would later co-found synthesizer company Ensoniq. Yannes criticized other contemporary computer sound chips as "primitive, obviously (...) designed by people who knew nothing about music." Often the game music became a hit of its own among C64 users. Well-known composers and programmers of game music on the C64 were Rob Hubbard, David Whittaker, Ben Daglish, Martin Galway and David Dunn among many others. Due to the chip's limitation to three channels, chords were played as arpeggios typically, coining the C64's characteristic lively sound.

• On address $FFF6-$FFF9 (65526-9) in the C64 KERNAL, right before the hard-coded jump vectors for the processor, you can find the letter sequence "RRBY". These are the initials of Robert Russell and Bob Yannes, the two main engineers that created the C64.
• The Commodore 64's BASIC V2, the programming language which came built-in with the computer, can be crashed by executing PRINT""+-[x] (where x is any integer), or by attempting to create a BASIC program with an initial line number near 350800.
• Due to a quirk in the C64's BASIC operating system, an Easter egg or screensaver of sorts may be activated by pressing the RUN/STOP and RESTORE keys in unison, then entering POKE781,96:SYS58251 on the subsequently cleared screen.^[5]
• There is a way to hide lines of code written in the BASIC Language stored in local memory. It involved using the "heart" symbol.
• Entering the character shift-L (which looks like an L-shaped border corner) into the program code will cause a syntax error when that line is LISTed. This is a simple way to prevent arbitrary listing of the program code.