Market research firm The NDP Group has issued a report that says Web users who are active on social networking site Twitter are more engaged with music and, more importantly, tend to be more likely to purchase music online. The firm bases these conclusions on less than 4,000 completed surveys for its quarterly music-acquisition study. First, the engagement: according to the report, one-third of surveyed Twitter users listened to music on a social networking site, 41% listened to online radio (compared to 22% among all Web users) and 39% watched a music video online (versus 25% among all Web users) during the first quarter. Twitter users are also said to be twice to visit services like MySpace Music and Pandora than average Web users.