What was the age of the youngest symphony composer?

Answer 1

W A Mozart was composing at the age of 4 years. I personally know of no younger composers.

Another answer:

This is not the sort of question that can have an exact answer. In the case of most composers there is no hard-and-fast indication of how old they were when they first wrote something. You also have to bear in mind that there may not be a clear dividing line between childish jottings and 'composing' - how do you know when the one becomes the other?

Answer 2

The youngest symphony composer is Wolfgang Amadeus Mozart. He began composing at the age of six and wrote his first symphony at the age of eight.