I record so the loudest portion is -12db, and boost the quiet parts in post. The boost is gradual, between songs, and is usually spans 10sec or more. I can't speak for Audacity, but in Goldwave, you boost between cue points linearally, e.g., a straight line boost of 20% or so over a 10 sec span. Then continue that boost for the accoustic song, and do the reverse on the next track, assuming it is electric.