I'm not really sure what you guys are trying to do....
but pdaXrom with 2.6 era kernels had full sound equalizer support
quite a long while before pdaXii13 did - so it must be possible with newer kernels
(if configured properly)
/dev/sequencer is a little more tricky, since Zaurii don't have any FM sound hardware
or anything directly supporting MIDI.
I don't think any stock kernels (for OE/angstrom/pdaXrom) have this enabled and working,
but you CAN build an ALSA kernel with timidity softsynth sequencer support.
I've done so, and it works [sufficiently long ago that I can't remember all that I did to get it going]
Also.... quite slow, and it *will* impact overall responsiveness.
Programs that send waveform samples to the sound chip should work fine, with standard ALSA support
(or if they use OSS /dev/audio, ALSA with OSS compatibility enabled)
Programs that send FM instructions, or MIDI frames to the sound chip
will require some more effort- this is nothing new with Titchy, or 2.6 kernels, just facts of life.