Online music revenue globally is set to reach $6.3b in 2011, up from $5.9b in 2010, according to Gartner. The technology research firm expects worldwide online music revenue of $7.7b in year 2015.

However, Gartner sees revenues on physical music (CDs and LPs) to plummet to about $10b in 2015 from $15b in 2010.

Gartner research vice president Mike McGuire said, "As consumers opt for connected devices — media tablets, smartphones and connected media players — across world regions, their desire for access to and consumption of music and content is growing as well."

The last decade has seen CD sales steadily declining as digital downloads and streaming music services are spurring the online music industry sales, Gartner says.

It estimates that subscription services will account for 29% of end-user online music spending in 2015.

With online music in North America maturing, the double-digit growth rates will be harder to sustain there, while the highest growth rates will be witnessed in Latin America, the Middle East and African regions.