The sound of two pianos

A few days after the passing of Earl ''Fatha'' Hines, the distinguished jazz pianist Dave McKenna gave a solo concert at Brown University. It was a torrentially rainy evening, with water sluicing down both sides of the street, and ticket-holders - their umbrellas waggling wildly - leapfrogged one roiling stream after another to arrive at the scene, an old brownstone building, with access to the stage through an organ loft.

Mr. McKenna, a large, placid man, with slicked-down hair that makes him always look as if he had just come in from the rain, played a medley of significant titles, from ''Here Comes That Rainy Day'' to ''Singing in the Rain.'' He also gathered together a set of songs on friendship. ''Can't We Be Friends?'' ''This Is The End of a Beautiful Friendship'' - the sweet and plaintive sentiments filled the air.

Mr. McKenna is a pianist who extends his instrument from delicate lyricism to striding exuberance, but as a personality he practices New England restraint. He acknowledges the existence of an enthusiastically applauding audience by little sidewise nods of the head - no eye contact. He does not bother to announce his song titles, and certainly avoids any peroration on program themes of the sort favored by some musicians too weak to resist the temptations of a microphone and a captive audience. When the subject was rain, there was *k need to explain. When the subject was friendship, who knows whaT prompted it?

But a listener can be permitted to imagine that, having serenaded the weather , Mr.McKenna was offering an equally timely salute to ''Fatha'' Hines - a friend surely to every jazz pianist who came after him.

Among critics, talk about ''influences'' comes cheap. But there are only a few true originals in the history of any art. In jazz the trumpet simply cannot be conceived of without Louis Armstrong, nor the piano without Earl Hines. Playing together over a half century ago, they invented the voices of their instruments so masterfully that one must divide the history of jazz trumpet into Before Armstrong and After Armstrong, and the history of jazz piano into Before Hines and After Hines.

Listening to Armstrong and Hines on their 1928 recordings, ''West End Blues'' and ''Weather Bird,'' the ear measures a quantum leap. The piano - hitherto the thump-box of the rhythm section or the obedient servant of the dictatorial strum of ragtime - suddenly emerges under Hines's fingers as a sophisticated solo instrument, full of astonishing grace notes, spirited internal dialogues, and spectacular time-changes.

Art Tatum, Teddy Wilson, Erroll Garner,"OscarPhy yO m Kt is impossible to imagine later pianists without Hines occupying the giant middle-ground between them and the future and Jelly Roll Morton and the past.

In fact, Hines became his own future. When he was still only in his mid-30s, the man who had once charmed Al Capone in Chicago with his Dixieland beat was playing beside Dizzy Gillespie and Charlie Parker and Thelonious Monk at Minton's in New York, helping to preside over the birth of ''bop.''

Except for a brief dry period, Hines seldom repeated himself and would have disapproved of being copied by others. A bit of an original himself, Mr. McKenna cannot be interpreted as a ''disciple'' of Hines, or anybody else. But on this evening of drumming deluge in Providence, R.I., the ear chooses to hear echoes on its own. At his most inspired, Hines could play arpeggios that seemed to leap right off the end of the keyboard. Just for this once, they seemed to land, notes flying, on Mr. McKenna's piano.