Born in Düsseldorf, Croll studied Kapellmeister at the Robert Schumann Hochschule and musicology with Rudolf Gerber at the University of Münster.
His research on Salzburg's music history and its lively cultivation was directed not only at Wolfgang Amadeus Mozart but also at Johann Michael Haydn, Heinrich Ignaz Franz Biber, Georg Muffat among others.
Through his personal commitment he was able to acquire a number of important collections and estates (Rudolf Gerber, Bernhard Paumgartner, Friderica Derra de Moroda) for the institute.
An intensive professional exchange took place with musicians and conductors such as René Jacobs, Alan Curtis and Diego Fasolis, and open-minded interpreters such as Nikolaus Harnoncourt could be won for lectures on performance practice.
The 'Collegium musicum' at the Institute of Musicology, which Croll had directed for many years, offered students the opportunity to explore the subject of their field by making music themselves.