Apple wants to help you name that tune. The company is planning to unveil a song-discovery feature in an update of its iOS mobile software that will let users identify a song and its artist using an iPhone or iPad, said two people with knowledge of the product, who asked not to be identified because the feature isn’t public. Apple is working with Shazam, whose technology can quickly spot what’s playing by collecting sound from a phone’s microphone and matching it against a song database. Apple is bolstering its music offerings even as song-download sales have slowed across the industry. While the Cupertino, California-based company is the world’s largest music seller through its iTunes store, customers are listening more to Internet services like YouTube, Spotify and Pandora.