ROCK/POP. Boston - Walk On. (MCA): If you're one of the many fans who has spent most of the past decade waiting for Boston to release a new album, you'll have to keep waiting. Although Tom Scholz credits fellow band members with helping him, ``Walk On'' is more of a solo effort. @CDText = It's a fair attempt at a comeback, but the album would have been stronger if it had been a complete effort by all its members. Noticeably missing are Brad Delp's lead vocals that helped carry Boston's past songs to the top of the charts.