Dessauer was born in Würzburg, the son of Guido Dessauer and his wife Gabrielle. He received his Abitur at the Kolleg St. Blasien in 1974. He then studied church music at the Richard-Strauss-Konservatorium in Munich for a year, studying organ with Elmar Schloter. From 1975 to 1980, he studied church music and concert organ at the Musikhochschule München with Diethard Hellmann and Klemens Schnorr. He continued his studies with Franz Lehrndorfer and received the Meisterklassendiplom (master class diploma) in 1982. He was a member of Karl Richter's Münchener Bach-Chor.
Dessauer was the organist at services at the Kolleg St. Blasien 1971–1974, then at the Akademie Tutzing for one year and conductor of the choir of the Protestant parish Tutzing, 1975–1981 cantor of St. Andreas, Munich.
From 1981, he has been the cantor at St. Bonifatius, Wiesbaden, the central Catholic church in the capital of Hesse. He is the conductor of the 107-member Chor von St. Bonifatius, founded in 1862, of the children's choir Kinderchor von St. Bonifatius, and of the Schola for Gregorian chant. The church choir sings at services, including regular orchestral masses of Haydn, Mozart, Beethoven and Schubert for Christmas and Easter, accompanied by members of the orchestra of the Hessisches Staatstheater Wiesbaden, with soloists from the Hochschule für Musik Mainz such as Andreas Karasiak and students. In 2011 they performed the Mass No. 1 in B-flat major by Johann Nepomuk Hummel, in 2012 the Missa "Dixit Maria" by Hans Leo Hassler. On Dessauers initiative, the organ built in 1954 was improved by Hugo Mayer Orgelbau in 1985.
Every year, typically on 3 October, German Unity Day, Dessauers has conducted a choral concert of such works as Mendelssohn's Elias, Ein deutsches Requiem of Brahms, and Verdi's Messa da Requiem. Both Chor and Kinderchor appeared in performances of Hermann Suter's Le Laudi (1998 and 2007) and in 2004 in the German premiere of John Rutter's Mass of the Children. In 2006, Dessauer conducted Karl Jenkins' Requiem, composed in 2004. In 2010, he chose works of Bach, his Mass in G minor and choral movements from cantatas BWV 140, BWV 12, BWV 120 and Wir danken dir, Gott, wir danken dir, BWV 29. In 2011 he conducted Haydn's Die Schöpfung. The children's choir sang along with the soprano.
To celebrate the 150th anniversary of the choir in 2012, Dessauer commissioned Colin Mawby to compose the Missa solemnis Bonifatius-Messe. Mawby wrote the Mass in 2011 for the forces available at the church, soprano, choir, children's choir, oboe and organ, premiered on 3 October 2012. The organist was Ignace Michiels from St. Salvator's Cathedral in Bruges, soprano Natascha Jung, oboist Leonie Dessauer. A second performance was on 3 November in the Frankfurter Dom, with organist Andreas Boltz. In 2013 he performed Schubert's Mass No. 6 along with his Unfinished Symphony. The concert of 2014 was John Rutter's Magnificat.
Dessauer first continued the tradition of a monthly concert Stunde der Kirchenmusik ("hour of church music"), and then instead began a series Boni-Musikwochen, grouping choral and organ concerts around a theme within a week or two. The Musikwochen 2010, Reger und mehr ("Reger and more"), presented concerts of Kent Tritle and Ignace Michiels, among others.
Dessauer appeared with the Chor von St. Bonifatius in Azkoitia and San Sebastián, in both churches at a Cavaillé-Coll-organ (1986), at the Limburg Cathedral (1987), in St. Jakobus, Görlitz (1990) and in Memphis, Tennessee (1996). They appeared in Rome in 2008, when they performed Vivaldi's Gloria and Haydn's Nelson Mass in San Paolo entro le mura in concert and sang during mass at St. Peter's Basilica.
Dessauer has appeared in recitals in Europe and the U.S., at the Washington National Cathedral and St. Patrick's Cathedral, New York. He played the Kotzschmar Organ at the Merrill Auditorium in Portland, Maine, and in the Cathedral of Our Lady of the Angels in Los Angeles. In 2004, he lectured at the National Convention of the American Guild of Organists in Los Angeles on the choral music of Max Reger, who was a member of the parish of St. Bonifatius while he studied and lived in Wiesbaden. In 2005, Dessauer played at the Spreckels Organ Pavilion in San Diego. In 2010, he gave a recital at St. Ignatius Loyola, New York.
From 1992 he has conducted events for the Rheingau Musik Festival called "Orgeltour" (organ tour), visiting historic organs in the region. The first tours covered historic organs of the Rheingau, later ones extended to the cathedrals of Worms and Speyer, Würzburg and Fulda.
Dessauer played until 2010 a regular concert on New Year's Eve at the Walcker organ of the Marktkirche, Wiesbaden, together with its organist Hans Uwe Hielscher. To celebrate Liszt in 2011, he played three major organ works of the composer on the instruments which was built around the time of the compositions, Fantasy and Fugue on the Theme B-A-C-H, Variations on Bach's "Weinen, Klagen" (1863), and Fantasy and Fugue on the chorale Ad nos ad salutarem undam.
In 2014 he toured in the US, playing concerts at the Washington Cathedral, at St. Mary's Cathedral in San Francisco, California, and at the Salt Lake Tabernacle organ in Salt Lake City.
From 1995 to 2013, Dessauer was an organ teacher at the Hochschule für Musik Mainz, part of the Gutenberg University in Mainz.
In 1985, Dessauer invited singers to form a choir in order to perform a single work, the Hebbel-Requiem of Max Reger in the organ version of the Munich organist and composer Max Beckschäfer. The name Reger-Chor was chosen in 1988, when the next project was dedicated to the German premiere of Joseph Jongen's Missa op. 111. Later projects included one of the first performances in Germany of Rutter's Requiem, recorded on the first CD of the Reger-Chor in 1990. In 2001 an international collaboration began with the organist Ignace Michiels, bringing together an almost equal number of singers from Flanders and the Rhein-Main Region to perform an annual concert both in Germany and Belgium. In 2003 he conducted the premiere of the organ version of Reger's Der 100. Psalm by François Callebout.
In addition to works of Reger, Dessauer chose rarely performed church music of composers such as Herbert Howells, Benjamin Britten, Herbert Sumsion, Maurice Duruflé, Edward Elgar, Frederick Delius, William Lloyd Webber, Jules Van Nuffel, Joseph Ryelandt, Andrew Carter, Kurt Hessenberg, Rupert Lang, Morten Lauridsen and Eric Whitacre. In 2015 he conducted Bach's Missa in B minor, BWV 232 I, from the newly-edited parts for the Dresden court, with members of the orchestra of the Hessisches Staatstheater Wiesbaden.
In 1999 he collaborated with Ignace Michiels, organist of St. Salvator's Cathedral in Bruges, in a project to bring jointly to a close a century of violence. Both in Bruges and in Wiesbaden a concert was performed by the choirs Cantores and Chor von St. Bonifatius, Michiels playing the organ and Dessauer conducting. The concert in Bruges on 23 October 1999 was named Eeuw van zinloos Geweld (Century of meaningless violence) and expressed it in Maurice Duruflé's Prélude et Fugue sur le nom d'Alain, Jules Van Nuffel's In convertendo Dominus, Jehan Alain's Litanies, Rudolf Mauersberger's Wie liegt die Stadt so wüst, Gerald Hendrie's Exsultate from the sonata In praise of reconciliation, and Duruflé's Requiem. The concert in Wiesbaden was called Versöhnungskonzert zum Ende des Jahrhunderts (Concert of reconciliation at the end of the century).
In 1995 Dessauer prepared the choir for a memorial concert for the 50th anniversary of the end of World War II, On 8 May 1995, Britten's War Requiem was performed in a ceremony of the government of Hesse at the Kurhaus Wiesbaden, with choirs from countries who were opponents during the war, the Swindon Choral Society from Swindon, UK, the Macon Civic Chorale from Macon, Georgia and the Schiersteiner Kantorei, conducted by Martin Lutz. A year later they took part in a performance of the work with similar forces in Macon.
In November 2009 he performed again Duruflé's Requiem, this time with a choir of volunteers who wanted to remind of the Holocaust, in a Gedenkkonzert gegen Antisemitismus, a concert against Antisemitism. Janina Moeller sang the mezzo-soprano solo, Petra Morath-Pusinelli was the organist.
In November 2015 he was the organist for a sing-along organised by the Diocese of Limburg in St. Bonifatius. A choir of 150 volunteers studied Gabriel Fauré's Requiem and performed it as part of the festival Wiesbadener Bachwochen, and Dessauer played in contrast Olivier Latry's organ meditations Salve Regina, in which, according to a reviewer, he made the listener feel the complete cosmos of humanity, including the cruelty and violence, from which to be freed the prayer requests ("den gesamten Kosmos des Menschlichen nachempfinden ließ, einschließlich der Grausamkeit und Gewalt, aus der in diesem Gebet um Errettung gebeten wird").Kontraste (Contrast), Gabriel Dessauer at the Mayer organ of St. Bonifatius
Orgel-Feuerwerk I – V (Organ Fireworks)
Just for Fun, Organ Historical Society Catalog
John Rutter: Requiem, motets of Reger, Reubke's Sonata on the 94th Psalm, Reger-Chor, Monika Fuhrmann (soprano), instrumentalists, organist (Rutter): Petra Morath, organist (Reubke) and conductor Gabriel Dessauer (1990, recorded live in St. Bonifatius Wiesbaden)
Romantische Orgelkonzerte, Marco Enrico Bossi: Organ concerto A minor op. 100, Josef Gabriel Rheinberger: Organ concerto G minor op. 177, Léon Boëllmann: Suite Gothique op. 25, Kammerphilharmonie Rhein-Main, conductor: Jürgen Bruns (1997)
Hermann Suter: Le Laudi, Zofia Kilanowicz, Pamela Pantos, Andreas Karasiak, Johann Werner Prein, Chor von St. Bonifatius Wiesbaden, Kinderchor von St. Bonifatius, Witold Lutoslawski Philharmonic Wroclaw, 1999
Max Reger: Hebbel-Requiem, organ works, Reger-Chor-International, conductor Gabriel Dessauer (2001, recorded live in St. Bonifatius Wiesbaden)
Max Reger: Der 100. Psalm, Introduction, Passacaglia and Fugue in E minor op. 127, Reger-Chor-International, conductor Gabriel Dessauer (2003, recorded live in St. Bonifatius Wiesbaden)