MIXED MEDIA : *** “LIVE ON BROADWAY” Barry Manilow <i> 6 West videocassette ($19.98)</i> : Items in this survey of pop-related videos, books and laser discs are rated on a scale of one star (poor) to five (a classic).

Manilow appeals mainly to the straight-laced, over-35 crowd that prefers ballads brimming with melodrama--the chief ingredient in Manilow staples like “Mandy” and “I Write the Songs.” That audience should love this swiftly-paced, well-produced, 90-minute tape of Manilow’s Broadway show--with the songs structured around key points in his life and career. Though mainly a solo show, Manilow uses supporting performers for several numbers. Never an exceptional singer, he makes maximum use of his strengths--earnestness, an amiable personality and a knack for making his audience feel warm and comfortable.