The TIA chip is responsible for both the audio and visual graphics of the Atari 2600. On the audio side, it has 2 oscillators with 16 different types of "waveform" each. Each oscillator has 5 bit pitch depth with 32 separate values. This results in some very out of tune tonal pitches. Also, each "waveform" is tuned differently, relative to the tuning values.
How to make TIA music
Paul Slocum's Sequencer Kit 2
The most popular TIA music driver out there. Use it to write your music directly in assembly. Hard as a brick in usage, but good for getting the most out of your 4K ROMs.
torTIA
torTIA is an .IT to TIA converter by lupe, written in Python, and based on Paul Slocum's kit. Write your music in OpenMPT with a specially prepared .IT module that gives you a very good idea about how the music will sound on the actual console. Arguably the most comfortable TIA tool around, but unfortunately it's rather limited: For the time being, the maximum song length is 512 rows, and there is no proper volume support.
it2tia
Another Python .IT to TIA converter, made by GreaseMonkey. Also comes with an .IT template with sampled TIA waveforms, but unlike torTIA, it does not consider the peculiar TIA tunings. It does have volume support, however.
Visual bB Music Editor
The Visual batari BASIC IDE has a music editor built in. Unfortunately it doesn't optimize the data at all, so unless you know your way around Batari Basic, you'll run out of memory very quickly.
Links:
Sound programming guide via Paul Slocum here.
