With a single tap, the Twitter Audio Card lets you discover and listen to audio directly in your timeline on both iOS and Android devices. Throughout your listening experience, you can dock the Audio Card and keep listening as you continue to browse inside the Twitter app. We’re launching this new audio card in partnership with third-party streaming services. The first partner for streaming on Twitter is SoundCloud."
SoundClouds write in their blog: "In the coming weeks, we’ll be making the cards available to anyone who posts on SoundCloud. Everyone using Twitter on mobile will be able to hear what you’ve shared right there in their timeline."
Read the original Press Release here, with a list of SoundCloud partners who you can listen to. One of the partners are of course iTunes.