The Jimmy Page [ tickets ] and the Black Crowes [ tickets ] single "What Is and What Should Never Be"--available only by download or mail-order--has entered three rock charts, making it the first hit single distributed exclusively by an online music retailer.

The track, which is on Musicmaker.com's double-CD "Live at the Greek," is in the top 10 on the Radio & Records rock chart. It is also No. 6 on FMQB's Mainstream Rock Chart and No. 15 on Billboard's Mainstream Rock Tracks chart.

Some brick-and-mortar retailers have complained that they aren't able to sell the album in stores, while radio stations which promote the album on the air have been able to take a cut of sales revenue by linking to the Musicmaker.com website. Jimmy Page's manager Bill Curbishley told Billboard that he didn't want to release a physical CD at the same time Atlantic was releasing "Latter Days, Best of Led Zeppelin 2," which came out on March 21.