What if you could whistle a melody to the phone and the app would find out what melody you whistled. It could be an easy way to find songs if you had forgotten which song or artist you was looking for.
It looks like your idea was posted a while ago but, unfortunately, it hasn't gathered the minimum amount of votes to stay active in the Ideas Exchange (50 votes in the first 3 months). I'll mark your idea as "Closed - Not Enough Votes". You can learn more on how the Ideas Exchange works here.