Abstract: Methods and apparatus for reducing replays in the recording of live musical performances, and for other recording purposes, are disclosed. The apparatus includes novel audio frequency electrical signal processing devices which can be incorporated in re-recording systems by means of which "flat" recordings of original "live" instrumental and musical performances are re-recorded via effects boxes and instrument amplifiers which are different or differently set than the equipment used in making the original "live" recording, and thus the resulting re-recordings have the same apparent sound quality as recordings originally made "live" through the same effects boxes and instrument amplifiers set in the same way. The disclosed signal processing device of the invention includes an output trim control and a ground lift switch. Also disclosed are re-recording systems of the invention, and re-recording methods of the invention.