Overdubbing is the technique of adding more tracks of sound to a recording that has already been taped. These days recording an album is a complicated and fiddly business so overdubbing (adding extra recorded sound to a song, especially in order to heighten the total effect) is essential. Overdubbing has led to additional practices. These include "tracking," where the ensemble arrangement gets recorded first and then the improvised solos are taped and inserted. "Layering" techniques have also been developed where each instrument can be recorded separately. Occasionally this is accomplished by recording sections separately – rhythm, solos, harmonies, lead vocals.