Piper Jaffray expects revenue from Apple's 20 iTunes Music Stores to account for 5 per cent of the company's revenue in 2006.

In a note to clients obtained by iLounge, analyst Gene Munster repeated his "outperform" rating and $52 share target on the company's stock.

"Assuming 133 million iTunes downloads in the June quarter and applying that across the reported 6.2 million iPod shipments, Apple is averaging 6.1 iTunes downloads per iPod" Munster said.

Applying future iPod sales estimates, he increase his predicted iTunes sales estimates to 1.365 billion from 877 million.

He added: "We see the successful launch in Japan as another indicator that pockets of untapped demand remain in the international market for digital music," iLounge reports.