The Prince George's Philharmonic is on the move, galvanized by its new conductor, Kenneth Kiesler, as its recent concert demonstrated. Clearly, the 26-year-old Kiesler, who took over this season, has won both the respect and good will of his musicians. Equally obvious are the challenging standards he is setting for them and the excitement with which they are responding.

One suspects that Kiesler is a conductor who stresses not only the how but also the why of playing notes. The result is music making that holds the listener's attention despite technical flaws.

The March program, considerably more interesting that much community fare, sandwiched a Haydn symphony between the 20th century works by Igor Stravinsky and Zoltan Kodaly. Kiesler showed a solid grasp of the music and a notable ability to communicate its meaning to the orchestra, which consistently played with intelligence and musicianship.

There was an altogether more professional air about the orchestra's approach. In terms of precision and accuracy it had made large strides thanks to Kiesler's clear signals and lucid pursuit of the line of thoughts in a work. Apart from the usual string intonation problems, which plague every community orchestra (and some professionals as well), the main difficulty was lack of projection in certain key passages. However, the orchestra, which has already improved enormously in that regard, will undoubtedly give more and more as its confidence grows.

The wit of the Stravinsky works was captured in crisp fashion. There was a lovely sense of line in the Haydn, and Kodaly's colorful "Hary Janos Suite" received a spirited performance. In the latter work actor James Sears made an engaging narrator.

With his talent, Kiesler may not be a part of the Prince George's County music scene for long. His own development will at some point outdistance that of the Philharmonic. It is well worth hearing the two while they are together. The Greenbelt Players

The newly formed Greenbelt Players are off to a thrilling start at the Greenbelt Cultural Center with Lucille Fletcher's eerie drama, "Night Watch." The play is a particularly apt choice for a first presentation in the old Utopia movie theater, which the Greenbelt Cultural Center is attempting to reactivate as its permanent home. Following its highly successful Broadway run in 1972, "Night Watch" was turned into a film with Elizabeth Taylor in the lead role.

Vacant until a few months ago, the old movie house is still very much in the initial stages of being reclaimed as a vaible performance space after three years of disuse. An active citizens groups, spurred on by the example of the Publick Playhouse's reclamation of the old Cheverly movie theater in Bladensburg, is working to accomplish a similar feat in Greenbelt and has raised $7,000 since December.

Director Angela Schreiber has assembled a capable and congenial cast who project the suspense of "Night Watch" with considerable skill. The plot revolves around the fears of a nervous and fragile woman named Elaine, who may or may not have seen bloody corpses in a window of the building opposite her house.

Further complications come from a romantic relationship between her husband, John, and best friend, Blanche, who may or may not be deliberately nurturing Elaine's hysteria. To find out who is doing whom in -- and someone does definitely get finished off -- you will have to see the play.

Despite over-reliance on the mannerism of rubbing her neck in agitation, Janet Cripe handled the ambiguities of Elaine's nature convincingly. Bruce Fleshman made a suitably deceiving husband and Judy Marshall brought exceptional polish to the role of the girl friend. In supporting roles, Judith Holland showed a sure sense of the emotional conflict in Helga the maid and John Lebkicher made an affable next-door neighbor.

For ticket information about the play, which runs Friday, Saturday and Sunday at 8:15 p.m., call 345-3916 or 345-9369. For information about the Greenbelt Cultural Center, which welcomes new members, call Conrad Herling at 345-9369.