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. In this manner, from eighteen (18) digitally prerecorded sounds of the preferred embodiment ninety (90) individually selectable and/or combinable sounds are made available. In either embodiment, natural or other sounds may be stored in loop or sound bite format in either or both of the internal and external memories. In a further sound relaxation and sleep-inducing embodiment, first and second preselected sound patterns selected respectively to mask sound and soothe the listener and to induce a state of deep relaxation that helps the listener to fall asleep may be selected by depressing combination mode select and sequential sound selector switches. In alarm mode, sound select and alarm check buttons respectively allow any sound of the library of prerecorded sounds (sound card or internal, single or mixed) to be selected as the alarm wake-up sound and one-touch alarm status display and audible alarm replay of any sound selected at wake-up volume in sound wake-up mode.