Musical waves lap N.Y.'s shores

From the East River to Long Island, from Manhattan to Brooklyn, musical waves are lapping New York's shores these early July evenings. Up in Central Park, Linda Ronstadt and Company are rehearsing Gilbert and Sullivan's "The Pirates of Penzance." Down at the South Street Seaport pier, couples can dance to Friday's swing orchestra or Saturday's disco -- or both.

Across the river, just south of the Brooklyn Bridge, Bargemusic will strike a classical note with weekend concerts of Schubert, Mendelssohn, and Dohnanyi. On Saturday, the Newport Jazz Festival will board the Staten Island Ferry for music by the Heritage Hall Jazz Band of New Orleans and Panama Francis and his Savoy Sultans. Meanwhile, the sweet sounds of "The Sound of Music" rise nightly from the oceanfront theater at Jones Beach. Manhattan Showboat Musical extravaganza. Conceived and produced by Robert F. Jani. Executive musical director, Donald Pippin. Choreographed by Linda Lemac, Howard Parker, Debra Pigliavento, Frank Wagner. The Rockettes choreographed by Violet Holmes.

Not to be outdone amid all this musical wavemaking, Radio City Music Hall has just launched "Manhattan Showboat" as its 1980 summer spectacular. A big, splashy pleasure cruise, the new entertainment is at its happiest when the incomparable Rockettes and the nimble New Yorkers strut their stuff.

As a catchall extravaganza, "Manhattan Showboat" resembles one of those jollities planned by a gung-ho cruise director determined not to leave out anything or anyone. The scenically massive vessel docks at the Music Hall stage in a cloud of steam. Meanwhile, the splendid orchestra conducted by Elman Anderson has been going through its own mobile maneuvers.

The course plotted by Captain Belle (Karen Anders) takes "Manhattan Showboat" on an excursion down the stream of memory. Reaching back over "the incredible 100-year legacy of New York and American entertainment," the crowded voyage of rediscovery includes glimpses of the circus (with a live baby elephant), nightclubs and floor shows, big bands, vaudeville, reviews, and musical comedy. The panorama commemorates a fleeting parade of show-biz luminaries stretching from Annie Oakley and P. T. Barnum to Carmen Miranda and the Marx brothers, from Scott Joplin to Benny Goodman.

There is even a "sing-along," with slide projections and a bouncing ball. But like everything else in this gigantic kaleidoscope, the catches are too snatchy. the vignettes of Broadway musicals probably come off best, and there's a fascinating hat dance done partly under black light.

"Manhattan Showboat" runs into a make- believe storm, which proves less hazardous than the shoals presented by its script. Everything in the production is on the customary Music Hall scale. There are costumes galore. According to a management statistics, the performers wear 450 hats. The on-stage river boat reportedly weights 5 tons. with such a ponderous entertainment cargo, it has difficulty keeping afloat.