Ringtones are currently a great source of revenue for carriers and record labels, but analysts question how long consumers will be willing to pay inflated prices for music clips. Once full-music downloads are available through cellular data networks, ringtones will have to evolve. High tech visionary and recording artist Thomas Dolby Robertson thinks record labels and carriers should think of ring tones as loss leaders, much like traditional singles, and use them to push sales of full-length music tracks and albums. Interview