Another question in site gave me an answer. It is not quite like the book that I mentioned in the comments. You don't need to identify the intervals between the notes (as the book required) but only whether the notes go up, down, or stay the same. So, I expect that you need a longer sequence in general but it works surprisingly well with even a short sequence. I just tested it with the first theme from the second movement of Beethoven's fifth symphony. I entered: *UURDDUD. The * represents the first note so I said that it went up twice, then repeated a note, down twice etc. The theme that I wanted was not the first hit but it was on the first page. Slightly confusingly, a later instance in the same movement that did not continue as I expected appeared first. To be sure that you have the right hit, you will need some ability to read music.
I am talking about the Contour Search in this site but the other functions may be useful as well.
I expect to become a frequent visitor.