You can even search for any track available on Rdio and use that for your reaction. For example I reacted to this awesome duck post with the song Rubber Duckie:
All of the song reactions appear right in the comment feed, allowing users to quickly play clips of the songs used to react. Non Rdio users can hear a :30 second preview, and Rdio users can hear the whole song.
This all reminds me of musical greeting cards - music used to send a message or convey a feeling. It's a very social way of illustrating how Rdio can be used to comment on and share content. It's also advertising that is native, novel, and enhances the user experience. We're proud of this very cool partnership and thrilled to work with the folks at Rdio and Horizon Media to make this a reality. Gizmodo has a nice write-up of the functionality, and we hope you'll give it a try through the beginning of next year while the campaign is live.