Here's the strangest request for help you'll hear for a while, I'm sure !!

If there are any (especially) classical music experts out there, you might be able to help me.

I have in my head the most sublime piece of Mozart music. I think its a Concerto but not sure (can't reliably identify the solo instrument from the music in my head)

I don't know its name. I can sing it accurately.

I want to know what it is, because in a short time, I want to be able to include it as one of the pieces of music, at my mum's funeral. (sorry, a bit morbid, but an impending reality for me)

Does anyone have any ideas about how to identify the piece just by hearing it sung?