Depends upon what you mean by `musical ability'.
Music is basically mathematical at its core, so someone who can write music - i.e. using notation - or analyse it, or write about it, will probably have a Venus-Mercury thing happening, or maybe Saturn could even be involved.
But for someone who has a lovely voice, or who just picks up a musical instrument and can instantly play it, then perhaps you're looking at venus-Neptune.
In my family-of-origin all my siblings were taken to a piano teacher for lessons. Of the 4 of us, only 2 of us continued with it because we appeared to have `talent'. We both have Mars-Neptune in close conjunction - he in Virgo in 12th, and me in Libra in 9th. That could just be coincidence, too. Both of us were also academic, whilst the other 2 were not. Perhaps it means nothing at all!
And FWIW, this particular sibling and I both became Maths teachers! Whenever I taught Maths, I found it useful to use music.