Well, if I were thus rationed in this article and could have but one adjective for George Gershwin, that adjective would be "ingenuous." Ingenuous at and about his piano. Once an occasional composer named Oscar Levant stood beside that piano while those sure, sinewy, catlike Gershwin fingers beat their brilliant drum-fire-the tumultuous cascade of the "Rhapsody In Blue," the amorous languor of "The Man I Love," the impish glee of "Fascinating Rhythm," the fine, jaunty, dust-spurning scorn of "Strike Up the Band." If the performer was familiar with the work of any other composer, he gave no evidence of it. Levant (who, by the way, makes a fleeting appearance in the new Dashlell Hammett book, under the guise of Levi Oscant) could be heard mutterIng under his breath, "An evening with Gershwin Is a Gershwln evening." "I wonder," said our young composer dreamily, "if my music will be played a hundred years from now." "It certainly will be," said the bitter Levant,"if you are still around."