The hardware sweep was especially suited for sound effects. The envelopes and length counters were evidently designed with both music and sound effects in mind, though in the end since you could get a lot more versatility (for both music and sound) by ignoring them and building software macros, most games did so.boomlinde, something that just occurred to me that's kind of interesting design-wise different between SID and 2A03: 2A03's oscillators are all clock dividers, i.e. you have some counter that puts out a pulse every N clocks, which then drives the waveform generator. The SID being an accumulator adds N to the accumulator on every clock, and the high bits are (almost) directly used as the waveform output. The 2A03 units all have another output stage. This is visible to the user by whether the frequency registers increase or decrease with pitch; some Famicom expansions accumulate: FDS, N163, VRC7, others divide: MMC5, VRC6, 5B. The ones that accumulate all happen to use wavetables, incidentally.
Quietust has a few visual 2A03 overlays on his page, this one diagrams all the chip regions he's determined the function of: http://www.qmtpro.com/~nes/chipimages/r … egions.png
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. I agree that whatever the cost of a wavetable, a triangle must have been an obvious choice over a sine for reasons that you already mentioned. Though, if they'd wanted a reasonable sine, I think they would have gone for something more complex than sixteen step 4 bit wavetable. Say, 6 or 7 bit output, double the period increment rate, and a 32 step half-sine LUT fed by the output of the existing triangle circuitry.