Matchbox twenty frontman Rob Thomas will release his as-yet-untitled solo debut in May via Atlantic Records. The set features a guest spot by singer/songwriter John Mayer on guitar on an unnamed track, according to Thomas’ spokesperson. Other songs tipped to make the cut are “Lonely No More” and “Ever the Same.”The process of writing for a solo project as opposed to a band has been a liberating one, Thomas said last March. “First of all, it doesn’t have to have two guitars, a bass and a drum on every song,” he said. “After a while you want to try something different. It’s all about not having a framework that you have to fit into. It doesn’t have to sound like a band.” The album will feature production by Virgin chairman/CEO Matt Serletic, who has worked regularly with matchbox twenty since its 1996 debut, “Yourself or Someone Like You.”The other members of matchbox have lately been busy with side projects, including guitarist Kyle Cook’s the New Left, which self-released its debut EP, “Let Go,” in late last year.