Mobile music recognition service Shazam today announced it has 50 million users worldwide and has attracted investment from Silicon Valley VC firm Kleiner Perkins Caulfield and Byers (KPCB). The growth in usage is up from 15 million in February and the company is aiming to achieve 100 million by the end of 2010. It claims to have been downloaded on the iPhone App Store more than 10 million times and is also available on BlackBerry App World, Nokia’s Ovi Store, Google’s Android Market and Microsoft’s Windows Marketplace for Mobile. Shazam’s technology allows users to identify songs by holding their mobile phone up to a speaker.

KPCB’s undisclosed investment is a significant boost to the London-headquartered company, as it is rare for Silicon Valley funds to look for growth opportunities in Britain. KPCB has previously invested in such heavyweights as Google and Amazon. Shazam previously raised £11.5 million from Acacia Capital and DN Capital, its initial investors, and has to date raised just short of US$20 million according to reports. A report in The Times notes that Shazam is profitable, generating revenue through several methods, including taking a cut on advertising revenue, earning a fee when customers buy a song using the application and by people paying to subscribe to a premium service.