Miss Keys' "No One" is RCA's first-ever gold-selling ringback tone, with 500,000 downloads, according to the label. Ringback tones are song clips that mobile users can choose to play when others call them. By way of comparison, "No One" sold more than 2 million master ringtones, which the called party hears. In total, Keys has sold 4.3 million mobile downloads of one sort or another-including ringback tones, ringtones, full tracks and bundled offerings, reports Billboard.
据此：
Ringback tones 是来电铃声
Master Ringtone 是彩铃