The invention relates to a disc for use in an apparatus for signal processing, which apparatus comprises a digital audio source and a record player with a turntable and an arm carrying a pick-up element which is arranged to play a conventional record. The disc during its use is placed on the turntable and is provided with a groove which can be lowered by the pick-up element, and which comprises a time-code signal wherein during use of the disc the said time-code signal controls the digital audio source.