The Symphony No. 2 of Howard Hanson is a fiery, pensive, brightly orchestrated and delicately energetic work that we do not hear nearly as often as its qualities would justify."Let Us Now Praise Famous Men" by Samuel Jones is a beautifully wrought evocation of the spirit of American folk music.

They were the highlights of a program, last night in the Kennedy Center Concert Hall, that brough together a wealth of fresh, enjoyable compositions that are seldom played and well worth playing. Also heard were charming if lightweight Concerto for Double Bass by Karl Ditters Von Dittersdorf, the finely evocative "Eos" for "english horn and strings of Lewis Collabro and Arron Copland's "Fanfare for the Common Man" the only work on the program that anyone in the small audience was likely to have heard recently in a live performance.

They were all played commendably (though some more so than others) by The Youth Symphony of the United States, an orchestra organized only last month and scheduled to disintegrate (at least until the next season) by the end of summer. It was not comparable to the Philadelphia Orchestras, but it sounded better than some small orchestras I have enjoyed. Its program was tastefully and thoughtfully selected, and music director Manuel Prestamo interpreted it with a fine sense of color and form.

The Youth Symphony, currently on its first tour, is designed as a summer learning experience for young musicians who will perform and have brief residencies in 11 cities from Houston to New York during the season, learning from some of the masters of their instruments who play for major orchestras. Thanks to imaginative programming, the tour can also be a learning experience for audiences, and it was very enjoyable one last night.

David Scott Allen, who soloed in the Dittersdorf concerto, showed a good grasp of the music's wit and grace but his instrument was often outbalanced by the orchestra. Jennifer Graham's English horn had more success cutting through the texture of Collabro's "Eos," and the moments of insecurity in her playing were few and slight.

There was one serious drawback, however.The program notes, which devoted much space to describing the orchestra and listing its staff and benefactors, said not a single word about the music. A program like this not only deserves annotation but, because of the music's relative unfamiliarity, virtualy demands it.