Friedrich Gulda, Claudio Abbado and the Vienna Philharmonic presented four piano concertos by Mozart on Deutsche Grammophon in the 1970s - all of them enjoy cult status today. After concertos no. 25 & 27 were already released as part of the Original Source Series and received an overwhelming response, concertos no. 20 & 21 now follow, distributed over 2 LPs to improve the audio quality. To mark its 125th birthday, Deutsche Grammophon started re-releasing legendary recordings in the highest sound culture: the audiophile vinyl series The Original Source. The sound differences to the original releases are considerable. The copies of this series are limited and numbered on 180g vinyl records and in a deluxe gatefold edition with original covers and texts, accompanied by additional photos.