To be fair, I didn't test it extensively, but the couple of times I tried it (on French songs, mainly) it failed.

I also don't fully understand the use case, except maybe if you listen to a lot of radio in a car?

At home the music that comes out of my speakers is music I already own; sometimes I listen to radio but even then it's usually faster and more certain to just go to the station's website to check what music was playing a few minutes ago, than to be able to launch Shazaam before the song has finished playing.

Now if I could sing into an app that would be completely different.

Ah. I've only tried in on English (language) songs. It's handy if you are out in a cafe or otherwise, public area and want to identify a song.

Singing into the app would be cool. In my ex-company, there were folks working on getting it to work for Karaoke. So you can hum a song and it'll figure out the right track for you to sing with. I don't know if there's a commercialised product like this.

To shazaam's credit, it identifies popular songs even in non-english languages (Bollywood, Italian, several French songs; anecdotal evidence anyway)