From 1930-33 he taught at the Berlin Hochschule , from 1944 to 1958 at the Guildhall School of Music , London and then at the conservatory in Bern , Switzerland . From 1930-33 he taught at the Berlin Hochschule , from 1944 to 1958 at the Guildhall School of Music , and then at the Musikhochschule KÃ ln ( 1957 â `` 82 ) and the Conservatory in Bern ( 1957 â `` 85 ) .