Not on iOS, at least. Just tap the microphone icon in the search box, and a button "Search a song" appears.

I've never understood why it's only part of the mobile apps, though, and not part of web search.

I just downloaded the Google app for iOS and this feature was missing until I force-closed and reopened it. Then it appeared.

I’m his worked for me as well. Otherwise it would just do a Google search for “what’s this song” which was very frustrating. At least the song came up, even though it was in Spanish which I didn’t know whether it was used to train the models/input they use before trying.

Works for me: click microphone icon in search field, then click "Search for a song" in the bottom.

I just did it on my android phone. It couldn't figure out the song though. It did try.