We had a strong suspicion that Twitter's new music service would figure into the company's "big announcement" promised for today, and that is indeed the case. The company confirmed on Good Morning America this morning that its #Music service will be launching on the web later today with a separate iPhone app in tow. As expected based on the company's acquisition of We Are Hunted, the service is focused largely on music discovery, letting you find music that's popular with your friends or those you follow -- specifically, music shared from iTunes, Spotify or Rdio at the moment. According to Twitter, the web version will be rolling out over the next few hours, with the service currently offered in the US, Canada, the UK, Ireland, Australia and New Zealand. Twitter also says that it hopes to roll the service out to Android devices in the future, but unfortunately isn't offering anything more specific for the time being.
Update: The iPhone app is now available in the App Store. If it's not turning up in searches for you, this link should work. Most should also now be seeing the web-based version at the source link below.