Classic rock songs take on modern form

— -- Billboard's chart of the top-selling digital download tracks reflects the hottest tunes of the day: Leading the most recent list is rapper Soulja Boy, whose debut, Crank That (Soulja Boy), is also No. 1 on the Hot 100, ahead of Kanye West, Nickelback, Timbaland and Fergie.

But dig deeper and you'll find classic-rock chestnuts from as far back as three decades, including Journey's Don't Stop Believin' and Lynyrd Skynyrd's Free Bird, a sign that baby boomers' love for the music of their youth goes on and on and on and on, no matter how modern the medium.

"When you see some of these older songs there, it is a reminder to you that it isn't just kids who are buying downloads," says Billboard's director of charts, Geoff Mayfield. "It is something adults are getting into, too."

Don't Stop Believin' sits at No. 81 and has been on the chart for 35 weeks — more than five months before it served as Tony's swan song on The Sopranos finale. Before that, it also appeared on Family Guy. "There is something ubiquitous about that particular song," Mayfield says. "It does seem to resonate with gray-hairs, but kids seem to dig it, too."

Other artists making the latest chart: Guns N' Roses (Sweet Child O' Mine, No. 119, 36 weeks on the chart), Survivor (Eye of The Tiger, 141, 88 weeks), Aerosmith (Walk This Way, 152), Bon Jovi (Livin' on a Prayer, 165), The Eagles (Hotel California, 190) and Queen (We Will Rock You, 183, and Bohemian Rhapsody, 192).

Sales spike after ads and additions to library

Virtually all rock music is now for sale digitally at online stores such as iTunes, eMusic and Rhapsody, except for notable holdouts such as The Beatles and Led Zeppelin. Classic rock songs may wind up on the charts after being used in commercials or included on an iTunes playlist, says David Card, analyst with Jupiter Research. "Some of these are evergreen titles that boomers maybe bought on vinyl (or) as CDs, and it's an easy way" to transfer them to portable music players, he says. "Or sometimes, it just hasn't been available and becomes available in a digital form."