Simplify the following text for a Grade 8 native English-speaking person.
Original: He was born Bruno Schlesinger , but began using Walter as his surname in 1896 , and officially changed his surname to Walter upon becoming a naturalised Austrian in 1911 .
Simplified: His name was originally Bruno Schlesinger but from 1896 he was usually known as Bruno Walter . Walter became his official surname in 1911 when he became an Austrian citizen .