The possibility of using underscoring* that may include music but which may also be in the form of a soundscape

Sound can be used to cover moments of transition e.g. between the scenes or to cover the placing of stage props.

From CD's to internet downloads. May form an obvious part of the action (such as a train arriving at the station) or may be in the background throughout (e.g. birds chirping)

Created on stage in the moment

The particular level of a voice, instrument or tune (high or low)

To move sound from once place to another

intensity of sound

Increase the levels

in sound, bringing another sound state up to completely replace the current sound state/change at which some levels are increased while others are lowered.

microphones placed along front of stage

a microphone hidden in the actor's clothes

the public address system or any sound system