What hum to search is
Hum to search means finding a song from its melody alone, with no lyrics or original recording. Google offers this in its own app. HumFinder does it on a web page, so it works without installing anything.
On iPhone or Android
Open humfinder.com in your phone's browser, press Hum a tune, and allow the microphone when asked. If you blocked it earlier, you can turn it back on in your browser's site settings.
On a computer
It works the same way with a built-in or USB microphone. If nothing is heard, check which input your system is using.
Does it keep my humming?
No. Your browser normally reads the tune and sends only that. If it can't, the recording is sent encrypted, read once, and discarded without being saved.