Helio is launching a mobile music store today, bringing its offering in line with other national 3G carriers. Helio will offers subscribers songs from a number of major labels for $1.99 per track, downloaded over the 3G network to the phone. This spring it will add a PC version of the music store that will offer downloads that can be played on the PC or phone for 99 cents. Like all Helio content, music can be gifted or begged. Members can sign up for alerts when music for a specific artist is added to the store. Helio also announced it expects to reach 100,000 members early in the second quarter. Fellow MVNO Amp’d announced it reached 100,000 subscribers last month.