Simplify the following text for a Grade 12 native English-speaking person.
Original: For nine years Mengelberg dominated the scene , although other conductors , among them Bruno Walter , Wilhelm FurtwÃ ngler , Igor Stravinsky , and Arturo Toscanini , led about half of each season 's concerts .
Simplified: He stayed there for nine years , although other conductors , including Bruno Walter , Wilhelm FurtwÃ ngler , Igor Stravinsky , and Arturo Toscanini , led about half the concerts .