Since 1991, a complete edition of all recordings in which Karlheinz Stockhausen has personally participated is being released on compact discs. Each CD in this series is identified by Stockhausen's signature followed by an encircled number. The numbers indicate the general historical order of the works. Stockhausen realised the electronic music and participated in these recordings as conductor, performer, sound projectionist, and musical director. He personally mixed down the recordings, mastered them for CDs, wrote the texts and drew the covers.