I tried to use different "query by humming" services but the percentage of false positives (when a service produced a list of melodies and no one matched yours) was really huge. And even if the melody was in the list and you tried to find it again with the same service (by humming the same tune) the probability of getting it in the list again was pretty low.

Anyway, I think the idea of query by humming is not a dead end. However, such a hypothetical service should somehow collect and use a database of different "hums".