Commercial WGMS-FM (103.5), after dumping a playlist that some classical music aficionados had described as "Top 40," has zipped past its noncommercial competitor WETA-FM (90.9), according to the spring ratings of listeners 12 years and older. The results are based on information from Arbitron's survey, which is deciphered by the Radio Research Consortium, a Silver Spring-based group that is paid by public radio stations nationwide.

WETA dropped sharply to a 2.3 share from winter's all-time high of 3.1 and was down from a 2.7 recorded during the spring of 1989. WGMS netted a 3.3 share, up from winter's 2.5 share.

WAMU-FM (88.5), featuring news, information, talk and bluegrass programming, held steady with winter's score, 2.2, but improved over the previous spring's 1.8 share. There has also been growth in the targeted adult audience.

"We have been at a 2 share or better since fall of '88, and except for the spring {1989} dip to 1.8, it's been bouncing between 2.0 and 2.2 each book," said WAMU program director Steve Palmer yesterday. "It's very heartening that the numbers have been very steady over the past six books."

But the Arbitron research shows WAMU with a dramatic increase of listeners for NPR's "Morning Edition" (with Bob Edwards) and the station's talk shows. "That's where the growth in audience has come," Palmer said. For instance, in the much-sought-after 25-to-54-year-old demographic, morning listenership in the spring ranged from a low of a 3.3 share during the 9 to 10 a.m. hour to a high of 6.3 in the 7-to-8 a.m. hour, up from winter's results.

Meanwhile, 6,500-watt WDCU-FM (90.1) and its 50,000-watt competitor WPFW-FM (89.3) continued to slug it out for listeners tuning in for jazz and community interest programming. WDCU repeated its winter score of 0.7 share, while the Pacifica-owned station dropped to 0.6 from a 0.7 share. During the spring of 1989 the stations scored 0.8 and 0.9 shares, respectively. This kind of scoring has been going on for several years between the financially strapped outlets and there's no indication it will change unless WDCU clears a variety of hurdles and powers up to 25,000 or 50,000 watts. Takoma Park's classical/religious WGTS-FM (91.9) again failed to get enough diary attention to register in the survey.

WGMS: What It Was, What It Is The "Top 40" playlist that had some WGMS listeners so irate was introduced late last summer. Programmers at WGMS, which has the nation's longest-running classical music format, suddenly introduced a narrowed playlist crafted from a study conducted by the Research Group. The Seattle-based consulting company had surveyed 600 Washingtonians between 25 and 54 years old. Along with the shortened music menu, the station rescheduled such specialty shows as Karl Haas's popular nationally syndicated program from its long-held afternoon spot to 11 p.m., and shifted recorded concert programming to weekends.

The changes brought scores of angry calls and letters to the Rockville studios. The shortened playlist also shattered on-air personalities' confidence in the product and caused chaos at the station, which slipped as low as a 2.4 share in the ratings. Morning host Dennis Owens, whose charming delivery and often mischievous discourse commands the respect of his competitors in all radio formats, was disillusioned and ready to walk.

"It was a 70-record hit parade and it got worse and worse," recalled Owens last week. "I was told to shut it down. We were playing only 30 or 31 minutes of music {out of every hour}. I made a re'sume', sent out tapes and began looking at something on the other side of the country."

But by January, program director Paul Teare, who in September had vehemently denied that an abbreviated list had been issued to staff announcers, began adding longer pieces to the playlist. (Teare recently recanted his September statement, adding that at the time he was under orders by the station's then-general manager to go by the research.) Slowly the ratings began to improve. In February Catherine Meloy was lured away from her top sales post at classic rock WCXR-FM (105.9) to take over as WGMS general manager. After several meetings with the unhappy on-air staff, the programming changes began with a reformulated "clock," the radio station's blueprint of what is heard -- music, news, traffic, weather, time, commercials, public service announcements and announcer ad-libs -- during any one hour of programming. Since then, there have been fewer commercials and a wider variety of music, and staffers say they are happier.

"We certainly have cleaned up the clock. We are playing longer pieces; we are playing concerts in their entirety, evening symphonies between 7 and 8 each weeknight," said the always perky Meloy. "We are giving people classical music in its entirety, which is something that they wanted."