Electronic instruments, primarily guitars, are known for their sonic signatures created with amplifiers. Rock music in the 1960s discovered the joys of the sound of an amplifier set to "10," where it created unique tone, but only at high volume levels. For the safety of the hearing of musician and engineer, amps are often segregated in other rooms, closets and even dedicated cabinets with speaker and microphone built inward. Loud volumes are then picked up by a rugged microphone and played back in a controlled way through studio monitors.
The human ear recognizes elements like time delay or volume differences in each ear to locate sounds around us, and also to tell us something about the space we inhabit. Is it a large room or small? Are there soft surfaces or hard surfaces? Often, speaker isolation removes these clues to give an engineer control over the sound scape later in the process. Aural clues are reduced to the microphone picking up the speaker output, not sound from the rest of the room.
Monitor speaker isolation takes a different form. Weighted speaker stands mechanically decouple the speaker from its room. When monitors are placed on a desktop, for instance, the desk itself may act as a resonator, adding overtones to what the speakers produce. Soffit mounting speakers eliminates sound reflections from the rear. These techniques allow more of the natural sound of the monitors to be heard directly by the engineer. Sonic details and stereo placement are easier to identify.
The power of multitrack recording is in the control offered at the mixing stage. Errors can be fixed and instruments emphasized or blended, but only when each track exists discretely. For ensembles playing at the same time, bleed from amplifiers into microphones on other instruments can ruin this separation. Speaker isolation becomes essential to regain control.