He graduated with the diploma as a certified music instructor (1984), the Artistic Diploma (1987) and the Concert Diploma (1989). In 1985 he took part in international master courses for piano in Austria and Switzerland. He received valuable input in an additional course of studies, a master course with Rudolf Buchbinder at the Music Academy in Basle. The friendship with the Russian pianist and conductor Igor Shukow of the famous piano school of Heinrich Neuhaus has been especially important for him.

Regular concert activities have led him through Germany, to Austria and Switzerland, to Denmark, Portugal, Spain, Russia and Hong Kong. He has performed among others at the Ruhrfestspielen and in the course of the Frankfurt Music Fair. Additional concerts have led him to Vienna, Zurich, Kaliningrad, Hamburg and Munich.

Radio and television broadcasts in Germany, Spain and Hong Kong have supplemented his concert activities. After a concert on Tenerife (2001) the radio station „Megawelle“ broadcast a two-hour portrait with and about Andreas Mühlen. In 2003 he performed the closing concert of the festival de Música Clásica in Adeje, Tenerife.

His repertoire includes works from a variety of styles and epochs. The seldom-performed early classical Toccata of the Portuguese composer Sousa Carvalho is part of his concert programmes as are Mussorgski´s Pictures at an Exhibition. He plays the sonatas of Haydn, Mozart and Beethoven, but also the Préludes of Debussy.

He often gives his concert programmes a specific motto. His programme From Beethoven to Spain establishes relationships which range from Beethoven´s Vienna classical period via the romanticism of Liszt and Debussy´s impressionism to Spanish dances.

His programme Piano Miniatures of Great Masters contains two characteristic pieces by Bach, Schubert, Chopin, Mendelssohn, Schumann, Liszt, Skrjabin and Rachmaninow respectively, which are related from a musical point of view. This way the listener experiences the development of the musical history of three centuries.

His recordings include one of the late piano pieces of Franz Liszt, which has been introduced by the Mitteldeutschen Rundfunk as ideal. His CD of the piano sonatas of Galina Ustwolskaja has met with the personal approval of the St. Petersburg-based composer who has attested „his exact and deeply felt interpretation“ of her works.