''In my heart I will always be a hopeless - no, make that a hopeful -romantic,'' Barry Manilow said at Tuesday's opening night show of his monthlong engagement at the Gershwin Theater on Broadway. The 42-year-old singer's confessions, like the rest of his remarks, were greeted with squeals by the loyal female fans who have been swarming to his concerts since he scored his first major hit 14 years ago.
The kind of fan loyalty Mr. Manilow inspires is extremely rare in popular music. And his endurance as a latter-day bobby-sox idol is a testament to his skill at projecting a boy-next-door ingenuousness while infusing sentimental formula songs of no particular depth with an appealingly homey sincerity.
Mr. Manilow's new show, directed by Kevin Carlisle, is a smoothly streamlined affair that has much less glitz than some of his earlier extravaganzas. Most of the first half is a musical autobiography that uses a park bench set, nonspeaking actors and slides of New York City. Threaded through the story of Mr. Manilow's ascendance from humble Brooklyn origins into the pop limelight are some amusingly self-effacing moments. Before he learned to play the piano, he recalls, he played the accordion. To prove it, he picks one up and plays ''Lady of Spain'' and fragments of ''Born in the U.S.A.,'' ''Bad'' and ''Like a Virgin,'' all reduced to a quaint, squeaky oompah.
In remembering his love for harmony groups of the 1950's and 60's, Mr. Manilow and his backup singers pretend he is a male member of the Supremes and one of Gladys Knight's Pips. Recalling his years playing the piano for theatrical auditions, he says he looked and acted like a ''geek.'' The story reaches a happily-ever-after ending with his first hit, ''Mandy.''
Near the end of the first act, Mr. Manilow reworks one of Liberace's most popular bits as he chooses a woman from the audience to join him onstage to sing ''Can't Smile Without You.'' As Liberace also used to do, Mr. Manilow continually reinforces his ties to his fans, thanking them profusely for their love and support and reminding them he is here only because of them.
Most of the second part of the evening is devoted to an extended medley of short excerpts from some two dozen Manilow hits, from ''One Voice'' to ''I Write the Songs.'' The way they seem to melt into each other underscores the essential sameness of so many of them. The ballads begin quietly and build up to drawn-out declamatory choruses. The most frequent lyrical themes are an adolescent longing for love and the satisfaction of having ''made it through the rain.''
Mr. Manilow doesn't oversell these greeting-card sentiments. At once gawky and cocksure, he states them plainly in a confident unaffected baritone that communicates an ingrained friendliness. The romance he offers is really not that of a lover but of a soulmate who at 42 still has stars in his eyes.