Are you:
Hip
See me once, with two joints, already half high
Hip joints, half way up your body.
See me twice, as a part of the toast that the people will cry
HipHip, Hooray!
See me once, at concerts, but not Bob Marley's
Concerts areyou see hip and happening, butat HipHop concerts. But Bob Marley's are hiphop, so being hip is seen too much?Marley does Reggae
See me twice, aren't these some cheerful parties?
HipHip, Hooray! (this time, at a party)