CD audio track != mp3. Either CD player would play audio itself (passed over analog audio connector), with the game occasionally changing track #. Zero CPU tim

CD audio track != mp3. Either CD player would play audio itself (passed over analog audio connector), with the game occasionally changing track #. Zero CPU time. Or a DMA controller would read digital audio from the CD, and CPU pass that on as-is to audio hardware. Lots of audio data streaming, but easy on the CPU.