 Beginning with Mantra for two pianos and electronics ( 1970 ) , Stockhausen turned to formula composition , a technique which involves the projection and multiplication of a single , double , or triple melodic @-@ line formula ( Kohl 1983 – 84a ; Kohl 1990 ; Kohl 2004 ) . Sometimes , as in Mantra and the large orchestral composition with mime soloists , Inori , the simple formula is stated at the outset as an introduction . He continued to use this technique ( e.g. , in the two related solo @-@ clarinet pieces , Harlekin [ Harlequin ] and Der kleine Harlekin [ The Little Harlequin ] of 1975 , and the orchestral Jubiläum [ Jubilee ] of 1977 ) through the completion of the opera @-@ cycle Licht in 2003 ( Blumröder 1982 ; Conen 1991 ; Kohl 1983 – 84a ; Kohl 1990 ; Kohl 1993 ; Kohl 2004 ; Stockhausen @-@ Verlag 2010 , 10 ) . Some works from the 1970s did not employ formula technique — e.g. , the vocal duet " Am Himmel wandre ich " ( In the Sky I am Walking , one of the 13 components of the multimedia Alphabet für Liège , 1972 , which Stockhausen developed in conversation with the British biophysicist and lecturer on mystical aspects of sound vibration Jill Purce ) , " Laub und Regen " ( Leaves and Rain , from the theatre piece Herbstmusik ( 1974 ) , the unaccompanied @-@ clarinet composition Amour , and the choral opera Atmen gibt das Leben ( Breathing Gives Life , 1974 / 77 ) — but nevertheless share its simpler , melodically oriented style ( Conen 1991 , 57 ; Kurtz 1992 , 192 – 93 ) . Two such pieces , Tierkreis ( " Zodiac " , 1974 – 75 ) and In Freundschaft ( In Friendship , 1977 , a solo piece with versions for virtually every orchestral instrument ) , have become Stockhausen 's most widely performed and recorded compositions ( Anon . 2007a ; Deruchie 2007 ; Nordin 2004 ) . 
