On one level, Younger Brother’s third album Vaccine seems an attempt to move away from the rarified atmosphere of psybient towards more mainstream realms. But more significantly, this thoroughly impressive work displays a real sense of artistic daring and vision. YB founders Simon Posford and Benji Vaughan remain trance-music auteurs, inserting quotes from their earlier projects with Shpongle and Prometheus throughout the album. The trippy glide of “Train,” the doom-struck twitch of “Sys 700” and the billowing pulsations of “Tetris” ought to please their hard-core faithful. Expanding Younger Brother’s sonic reach further are a batch of tunes in a prog-rock vein that fully utilize the talents of newly recruited guitarist Tommy Hamilton and drummer Joe Russo. “Safety In Numbers” — a jazz-tinged track combining an insinuating melody with cool cyborg chatter — is a good example of the group’s ability to work within classic song structures without losing their essence. Even better is “Night Lead Me Astray,” a yearning ballad showing off Ruu Campbell’s expressive vocals to full advantage.