'Tingalingalingaling!'

You don't have to be very old to remember how dramatic the Princess phone seemed when it was first introduced in 1959. Its slogan -- ''It's little, it's lovely, it lights'' -- was even farther ahead of the times than the phone itself, since that slogan describes most of the cellphones on the market today. The Princess was still just a Ma Bell phone, tethered to the wall. It had only one ring, and that ring was free. But you could argue that the Princess phone and its selection of muted pastels was one of the first big steps toward the world in which we now live.

It is a world in which consumers can spend, as they did last year, $3.5 billion downloading custom ring tones for their cellphones.

It would be one thing if all those people had bought all those ring tones because their cellphones came without the ability to ring. But every cellphone comes with several standard ringing sounds. Even that much choice would have seemed like a revelation in 1959. But nowadays a cellphone is the nexus for an endless emporium of stuff, including screen graphics and games. On the Web sites that sell ring tones, you can choose from among tones taken from popular music, from songs by Outkast or Linkin Park or dozens of others. Or you can download what one site calls ''real tones,'' like ''Shooting in a Panicked Crowd'' or ''Evil Chant.'' In some sense, this represents another step in the convergence of all small electronic appliances into a single tool. But the difference between downloading Ashanti's ''Rain on Me'' to your cellphone, for $1.50, and downloading it to your iPod for 99 cents is more than just a matter of acoustic fidelity. It's a matter of context.

To the music industry, whose global revenue is some $32.2 billion, ring tone sales are not inconsequential. To anyone who actually used a Princess phone, the thought of spending all that money on ring tones seems like the very definition of frivolity. But in our world, a teenager's frivolity is an executive's bottom line. The days when you could encourage your kids to save their allowance, as a form of economic virtue, may be long gone. They know all too well that consumer spending -- even on ring tones -- is what holds this economy together.