I played around with sound a lot on the A8 back in the day, in Atari BASIC, and I still remember that of the four parameters in the SOUND command, the third one was known as "distortion" and was an even number and determined if the type of sound was "tone (10)", "white noise (8)", or "distortion (12)".
I remember noticing that the range of the tones were 0-255, with 0 being nearly inaudibly high but as you went down, the changes in pitch were uncomfortably discrete and large, and I remember the lack of really low notes. The octave range (and pitch control) in this regard were woefully lacking. However, I played with distortion 12 and didn't think it was much use, and then I heard the first A8 game soundtracks to use the perfect musical scale found in 12 (in amongst the "off" sounds, if you know what I mean) and I was amazed at the distinct bass and quality they gave A8 sound, and I've loved Distortion 12 ever since then. Hence my example above, which I would swear uses two channels for that.