There is only 1 sound effect, which plays when a portal is used (as in that case Zampo is kind of suspended in a bubble). Other sound effects have been excluded by design to save CPU and RAM resources (as scrolling alone takes 81% of the CPU time and about 8 kB, and maps take about 30 kB).
That said, the soundtrack is very rich:
* it consists of 13 ditties and tunes: menu, intro, zone preamble, 5 zone-specific tunes, PIG-OF-GOLD mode, PIG-OF-STEEL mode, zone completion, game over, outro;
* for each zone, the music consists of 3 tunes: the zone-specific tune, the PIG-OF-STEEL mode tune and the PIG-OF-GOLD mode tune; the zone-specific tune acts as main tune, gets paused when either of the other two kicks in and resumes when it ends; the PIG-OF-STEEL mode tune has priority over the PIG-OF-GOLD mode tune; these tunes plus the game over ditty take about 4 to 5 kB (depending on the zone).