After the Graz Academy was opened in 1960, he received his vocal training there from the age of eighteen or nineteen with the soprano Herma Handl.
In 1964, he made his professional debut as an opera singer at the Staatstheater Braunschweig with the role of Count Almaviva in The Barber of Seville.
In April 1998 Hopferwieser sang his last performances at the Vienna State Opera: Herod and, as the last part, the first Geharnischten in Mozart's The Magic Flute.
In September 1973 he sang there, with Renate Holm as Marie, Hans in the opera The Bartered Bride as part of the reopening of the newly renovated Volksoper.
In 1975 he sang the officer Phoebus in the rarely performed, late romantic Franz Schmidt opera Notre Dame at the Vienna Volksoper.
[7] In the 1982–83 season he gave a guest performance on Opernhaus Kiel with the role of Walter von Stolzing (premiere: October 1982; conductor: Werner Saladin); he approached his role with "promising, somewhat baritonally colored material, which possesses particularly in the forte and in the high luminosity, in the mezzo-forte in the middle position sometimes slightly roughened, which has a slightly roughened effect".
[8] In October 1983 he made a guest appearance at the Badisches Staatstheater Karlsruhe in a concert performance of Wagner's early work Die Feen; he sang the part of Arindal.
At the beginning of the 1980–81 season he sang[9] Bacchus in Ariadne auf Naxos, in March 1986 Walther von Stolzing; furthermore he was a guest Drum-major in Wozzeck, with Karan Armstrong as Marie.
He sang abroad at La Scala, at the Teatro dell'Opera di Roma and at the opera houses in Lyon and Nancy.
[11] At the Scala, Hopferwieser was heard as Andres in Wozzeck (also with Ticho Parly and Mirto Picchi in the cast, conducted by Claudio Abbado, 1971) and in Cardillac (with Sir Donald McIntyre in the name part, directed by Ponnelle, 1987).
In 1981 the Polish label Muza released a live recording of the opera Fidelio in which Hopferwieser sings the part of Florestan.
On video a live recording of 1987 from the Bayerische Staatsoper was published, with Hopferwieser as Alfred in Die Fledermaus, with Pamela Coburn and Janet Perry, conducted by Carlos Kleiber.