After his Abitur, Xeiss studied musical composition with Hans Stieber and music theory with Franz von Glasenapp at the Staatliche Hochschule für Musik Halle/Saale from 1952 to 1955. Minor subjects were piano and viola. From 1955 to 1957 he studied composition with Rudolf Wagner-Régeny and music theory with Ruth Zechlin (harmony), and Jürgen Wilbrandt (counterpoint) at the Hochschule für Musik "Hanns Eisler" in East Berlin. In 1957 he passed his Staatsexamen. His critical remarks about the East German uprising of 1953 prevented him from becoming an aspirant in Berlin. From 1957 to 1959 he was instead for composition at Rudolf Wagner-Régeny at the Academy of Arts, Berlin. He received further encouragement from Paul Dessau.