Atari 2600 music: often out of tune?

[Gradualore]

I haven't yet written any code for the Atari 2600, so I'm below newbie so far. What I'm wondering just from playing several games in Stella is, how come a lot of soundtracks for these games sound out of tune? From reading the stella programmer's guide, it sounds like the frequency registers are 5 bit, does this really mean there are only 32 pitches that each sound channel can produce? Do these pitches just barely align on musical intervals, is that the problem? Then again that "Saigon" demo posted recently certainly didn't sound out of tune, but it sounds like it might be using some advanced techniques to give the illusion of there being more than 2 (??? correct?) sound channels at once, I'd imagine that technique could be used to alter the perceived pitch, too.

[Gradualore]

I haven't yet written any code for the Atari 2600, so I'm below newbie so far. What I'm wondering just from playing several games in Stella is, how come a lot of soundtracks for these games sound out of tune? From reading the stella programmer's guide, it sounds like the frequency registers are 5 bit, does this really mean there are only 32 pitches that each sound channel can produce? Do these pitches just barely align on musical intervals, is that the problem? Then again that "Saigon" demo posted recently certainly didn't sound out of tune, but it sounds like it might be using some advanced techniques to give the illusion of there being more than 2 (??? correct?) sound channels at once, I'd imagine that technique could be used to alter the perceived pitch, too.

 

I found this: http://www.classic-games.com/atari2600/vcssound.html Answers my own question. Probably should have googled first =D. Though, I didn't find any other topics on this particular forum about the subject. Anyone care to share how they work around this limitation?

[ilmarque]

Probably the best way to make songs to sound less out of tune is to choose notes that are somewhat in tune. The downside of this method is that you'll have a very narrow selection of notes to use. That's probably the reason why most of my 2600 songs sound pretty much the same

 

For Saigon I used Paul Slocum's music kit which i've been modifying a lot over the years. For example I've added a simple decay/sustain for both channels which makes the sound a bit smoother and may also give the illusion of having more than 2 channels. I've also added a simple vibrato, which simply varies the pitch of one channel between 2 values.

Edited January 10, 2011 by ilmarque

[RevEng]

See the "pitch picking" section of the do re bB document.

 

The intended audience of the document is bB coders, but most of it is general theory and links that apply to assembly coders equally.

Edited January 10, 2011 by RevEng

[diogoandrei]

Probably the best way to make songs to sound less out of tune is to choose notes that are somewhat in tune. The downside of this method is that you'll have a very narrow selection of notes to use. That's probably the reason why most of my 2600 songs sound pretty much the same

 

For Saigon I used Paul Slocum's music kit which i've been modifying a lot over the years. For example I've added a simple decay/sustain for both channels which makes the sound a bit smoother and may also give the illusion of having more than 2 channels. I've also added a simple vibrato, which simply varies the pitch of one channel between 2 values.

 

Wow, that's really interest about your version of Slocum's sequencer kit. Would you consider sharing it one day?

 

Best regards,

Diogo