Sony will launch its own iTunes alternative tonight, introducing a music and video download service at European trade event, IFA.

Set for announcement at a press conference this evening, Sony’s news comes as another Apple competitor, Archos, announced five Android-based tablet devices, ranging from 2.8-inch to 10-inch screens.

Sony will make its service available via the PlayStation3 and will later make it compatible with Walkman-branded MP3 players, Vaio PC’s, Blu-ray players, some televisions and Sony Ericsson-branded mobile phones. Even the PSP will get to become a peer in Sony’s content everywhere vision.

Amazon also intends introducing a subscription service, with the Wall Street Journal saying — in a remarkable reflection of another company’s mooted plans — Amazon’s service is focused initially on TV shows and movies rather than music.

Amazon is speaking about the service with NBC Universal, Time Warner, News Corporation and Viacom among others.

Despite the competitive moves all eyes will be on Apple’s keynote presentation tonight as expectation reaches new heights.