This morning I worked a bit more on getting sound smooth on the Raspberry Pi. I made a laserdisc image file where the audio is just a continuous sine wave playing "middle C". I observed two things:
a) when played with Dexter, the sound pops regularly so there must be a defect in my code somewhere
b) when played with ALSA test code, the sound is steady but there is a background buzzing noise that should not be present; this may be related to immature ALSA drivers
I will try it again later with "omxplayer" which is supposedly a high-performance media player to see if I can get the kind of sound I want, and if I can, I will just use the same approach for my stuff as they do.