U.S. cellular carrier Alltel Wireless and mobile application developer mSpot on Tuesday introduced a new service for wirelessly synching music stored on PCs to mobile phones.

Alltel's Music powered by Celltop is a service that lets subscribers access their music libraries from mobile phones. Celltop is Alltel's new technology, based on Qualcomm's Brew uiOne platform, which uses customizable "cells" to serve up content to subscribers. Cells are applications like call logs, text messaging, ringtones, news, weather, stocks, and sports scores that can be customized to appear on a phone's mail screen by clicking a phone's soft key.

Alltel initially rolled out Celltop on select phones last year and said it will have the technology on all new phones by the beginning of this year.

Music by Celltop uses software developed by mSpot, called Remix, which synchs music stored on PCs wirelessly to a phone. Subscribers can listen to the music as it's being downloaded. Remix then saves the music on the phone's memory card and more can be added depending on how much a memory card can hold, according to mSpot.

But it only works with music that is not protected by Digital Rights Management, meaning music that is not restricted to authorized viewing or playback of copyrighted material.

The service costs $4 with a one-month subscription or $10 with a three-month subscription and it's currently only available on Motorola's Moto Rokr Z6m phone. Alltel plans to launch the service on other Celltop-based phones in the first half of this year.

mSpot also supplies streaming radio software to Sprint, which the carrier offers to its subscribers as a re-branded service called Sprint Radio.

Mobile phones are increasingly packing in more features like digital cameras, media players, and even tools for creating blogs and posting content to social networking sites on-the-go. Music is among the most popular features that has become almost a standard on newer phones. Alltel and other carriers are introducing new music services in hopes of persuading consumers to move away from standalone media players to purchasing phones with such features already built in.