Pc sound? U6 has some music options but sound effects will be played through the pc speaker, in the case of dosbox this is emulated unless you turned it off in dosbox options.

pcspeaker=true. I get the music, but not the game sound effects (battles for instance are silent).

Not sure which sfx even exist, try in castle britain, next to a fountain and a grandfather clock.

Right, you should get battle sound on the pc speaker when you hit an enemy, or vice versa.

How many cycles do you use? Cycles=max or some too high number will probably make PC speaker sounds inaudible.