I often see the definite article being omitted in texts about famous people. For instance:
Towards the end of his life, avant garde composer John Cage turned to visual art
But I also see that it is equally frequently not omitted:
In 1944 the avant-garde composer John Cage wrote “Four Walls,” a 70-minute work using only the white keys of the piano
I am assuming that these are both valid. But why would you choose one over another? Is version 1 more "written" and version 2 more oral?
Edit: note that googling "by the avant garde composer John Cage" yields 3150 results and "by avant garde composer John Cage" yield 3760, so it's kind of inconclusive to say which is more common.