In one embodiment, an improved-customizability digital sound relaxation system having a sound card receiving port and a collectable sound card are cooperative to play prerecorded natural or other sounds by depressing one of a plurality of sound selector switches and a sound card selector switch. The new sounds of each collectable sound card customize the library of available sounds to individual taste. In another embodiment, an improved-flexibility digital sound relaxation system having at least two (2) prerecorded sounds stored at first and second memory locations of internal or external/internal memory devices may be selected and combined for concurrent and/or individual replay by depressing one of a plurality of sound selector switches and a combine switch, or by depressing one of a plurality of sound selector switches, a sound card selector switch and a combine switch.