Music marketing startup Onesheet has one big new feature and three new staff. The service, which helps artists create one webpage aggregating content from all the sites and social networks that they use, now has an iTunes widget available. Artists can now promote music, apps and e-books on their Onesheet page simply by typing in a URL on the Onesheet back-end. Meanwhile, the company has announced that David Andreone, Ryan Marshall and Jim Mulhearn are joining it in roles covering, respectively, industry relations, technology and marketing/biz-dev. Andreone was GM at MySpace Records, with roles at Columbia Records and Warner/Chappell before that. Marshall’s background includes Digg and the service that evolved into Groupon. Meanwhile, Mulhearn has been working at RootMusic.