A famous artist once claimed that all great art imitates nature.
Opposing Point
A famous artist once claimed that all great art imitates nature.
Premises
If this claim is correct, then any music that is great art would imitate nature.
But while some music may imitate ocean waves or the galloping of horses, for example, most great music imitates nothing at all.
Conclusion
The conclusion is implicit and it challenges the famous artist. Either the famous artist is wrong, or the principle is not applicable; if for example, great music is not necessarily great art. While this is not explicitly stated, it is implied by the pivot term “but.”