Extraneous sounds, picked up by a microphone. Generally used to describe the unwanted sound of one musical instrument as heard by a microphone in front of another instrument.
"The CD's of the older music took me back to a fun and carefree time of life. I enjoyed sharing the songs and stories with my children. Music can be a sort of history lesson. Because many events are marked by a song that stays in your mind. When the music is played a variety of memories return that otherwise might not have been triggered. ..."