◎石先広海（KDDI研）・Susan C. Herring（Indiana University）・服部　元・小野智弘・滝嶋康弘（KDDI研）

We analyze user behavior on SoundCloud.com, a web-based music distribution site, using the methodology of computer-mediated discourse analysis. The broad goal is to develop methods to facilitate communication among online users. In order to achieve this goal, we analyze SoundCloud comments, using speech act analysis and dynamic topic analysis. We address two research questions: What are the most common acts on the music distribution site, and which commenting function　contributes most to facilitating interactive commenting? Results indicate that site users tend to be more interactive when using the timed comment function provided by the site.