Born in Schiltach in the Black Forest, Frei studied music in his early years.
From age 14 on, well-known musical instrument factories such as Bruder, Gavioli, Mortier and DeVreese were employing him in Waldkirch and Paris.
Frei started maintaining organs, but noticed that many owners wanted something louder (thanks to the increased street noise made by early cars), and distinct (thanks to the wider availability of the record player).
Firstly he devised a new organ register called the "bourdon céleste," which replaced the high-maintenance clarinets and vox humana's with two rows of stopped pipes with very bright intonation, one row tuned slightly sharp to the other.
Into these he incorporated an amplified violin section by adding a violin-celeste stop, which was also tuned to this floating sound temperament.