Active as Thomaskantor after the German reunification, Biller returned the Thomanerchor to its original focus on church music.

[2] He studied at the Hochschule für Musik und Theater "Felix Mendelssohn Bartholdy" Leipzig from 1976 until 1981, orchestral conducting with Rolf Reuter and Kurt Masur, and voice with Bernd Siegfried Weber.

[5] After German reunification, he was a lecturer for choral conducting at the Hochschule für Musik Detmold[6] and at the Frankfurt University of Music and Performing Arts.

[2][7][8] Biller returned the Thomanerchor to the original focus on church music, which had been neglected while Leipzig was in East Germany; he established the choir in the liturgy of the Lutheran service and reintroduced Motette, a type of musical vespers service, in the Thomaskirche.

[1][3] The choir performed regularly three times a week there, Motette every Friday evening and Saturday afternoon, typically including a Bach cantata for the liturgical occasion, and Sunday service.

[10] From 2002, Biller was instrumental in the concept and new buildings for the boarding school of the Thomanerchor, the Forum Thomanum as a musical education campus (musikalischer Bildungscampus).