Willem Mengelberg
Born in Jülich, Germany, Stock was given his early musical education by his army bandmaster father. At the age of 14, he was admitted to the Cologne Conservatory as a student of violin and composition, where he counted composer Engelbert Humperdinck as one of his teachers and conductor Willem Mengelberg among his classmates. After graduating from the conservatory in 1890, Stock joined the Municipal Orchestra of Cologne as a violinist.