The Amstrad Plus range include DMA sound channels. Each HSYNC, 1 instruction per active DMA channel is read. Each channel executes an instruction which allowed looping and sending data to AY registers. Each DMA channel is effectively a AY register playlist and once started is executed without CPU intervention. It was meant to reduce the strain on the CPU.
This feature offered extra capabilities including 15Khz 15 kHz sample playback.
==Technical references==