If you're having trouble naming that tune, just fire up SoundHound to speak, sing, hum, or type out a song for the music-identification service to identify. The app is available in both a free version and a paid, ad-free version dubbed SoundHound Infinity.
Right when you open SoundHound, you'll see the big orange button up top. This is the key to the app's primary function. Give the button a single tap, place your mobile device up to a music source (or as close as you can get), and watch as SoundHound searches its enormous database for a match. You can put your device directly onto a speaker or just drop it on your passenger seat while your radio is playing. In either scenario, SoundHound should be able to do its job so long as the volume of the source isn't too low or too loud and distorted. Typically, the app needs between 3 and 10 seconds of "listening" in order to bring back any search results.
In my tests, I found that SoundHound was impressive in its ability to identify both popular music and slightly more obscure tracks. In this respect, I would say it is more or less on par with competitors such as Shazam. Of course, when it comes to any extremely niche songs, though, either app would almost certainly have some trouble doing its job. One thing that does set SoundHound apart from its competitor is its ability to identify songs that you sing or hum, which is perfect for those times when you get an unidentifiable song stuck in your head.