From 1942 he studied piano with a special permission with Grete Hinterhofer and musical composition with Joseph Marx at the Wiener Musikhochschule.
His war deployment as Luftwaffenhelfer and the subsequent emprisonment interrupted the musical career of Wilhelm, who returned to destroyed Munich in 1945 with a Notabitur.
Through the mediation of his brother Kurt Wilhelm who acted as assistant director for the play, the nineteen-year-old composer received his first commission.
The rhythm and sound schemata of Mars from the cycle of symphonic poems The Planets by Gustav Holst are now part of the standard stylistic repertoire of the film composers in Hollywood.
[2] He was married to the actress Helga Neuner, who became known to a wide audience through numerous theater appearances and the television series Die Firma Hesselbach.