Around the time Jones first acquired the station, WBMS, a daytime AM radio station that had programmed classical music, changed format. Jones decided to change WCRB's format from that of a typical suburban AM station of the era to fulltime classical music. FM service at 102.5 Megahertz was added by 1954 upon the purchase of the WHAV FM transmitter. FM brought WCRB's classical music format to parts of the Boston area that did not get good reception of WCRB's directional AM signal, and making improved audio quality available via the FM.
In 1961, WCRB-FM was the first Boston-area station to broadcast in multiplex stereo; for a few years prior to that, WCRB had broadcast some of its programming in stereo by carrying one channel on AM, the other on FM. WCRB was directly involved with the development of FM multiplex stereo. Station WCRB and H.H. Scott, then of Maynard, Massachusetts developed prototype stereophonic equipment that was used to prove the “General Electric” multiplex method being evaluated by the FCC. H.H. Scott was an early stereophonic receiver manufacturer that developed and manufactured high-quality home stereo equipment. Once the FCC approved stereophonic broadcasting, WCRB created a special “stereo” studio in downtown Boston, the first in the world. There was no dual channel (stereo) studio equipment at the time. Much of the equipment was hand-made by the engineering staff. Many can remember the call-letter announcements, made on the half-hour as required by the FCC; “You are tuned to WCRB, Waltham, thirteen-thirty AM, one-oh-two-point-five FM, with downtown studios in the elegant hotel Sheraton Plaza, featuring more than seventy hours weekly, of FM stereo programming.”
WCRB is noted for many other innovations. It was the first radio station to obtain a permanent waiver of the FCC rules requiring average modulation in excess of eighty-five percent. This was necessary to preserve the dynamic range of the concert music broadcasts. The station also obtained a permanent waiver of the FCC rule that required a station identification announcement every thirty minutes. This meant that a live concert performance no longer had to be interrupted for station identification.
The WCRB engineering staff worked with the National Association of Broadcasters (NAB) to codify the RIAA LP record frequency-response curve, and create the NAB standard. Other technical innovations followed. Before the early days of FM stereo broadcasting, nobody had encountered the necessity of amplitude- and phase-matching two 15 kHz stereo leased lines. The telephone company called such a channel type; “Program channel A.” To them, as long as the frequency response and noise level matched their specifications, stereo simply meant that there would be two lines. It was just a matter of labeling them! Not so. WCRB engineering worked with AT&T to generate a specification involving matching both the phase and frequency response. This became the standard of the industry. Eventually, as stereo caught on across the country, these methods and specifications were used to install stereophonic leased lines to transmitters across the country, until they were made obsolete by the development of composite-signal studio-transmitter links. In the early days of radio, stations had full-time engineers on duty. Therefore, the WCRB engineering staff also recorded live performances for the Boston Symphony Orchestra Transcription Trust.
Although Charles River Broadcasting had acquired other radio stations, WCRB remained as the company's flagship station.
In 1975, WCRB(AM) ended simulcasting of WCRB-FM, changing call letters to WHET, and its format to big-band/adult standards. In 1978, Charles River Broadcasting sold off WHET, but retained WCRB, which became increasingly successful over the years as a 24/7 classical music station.
WCRB was under a long-term commitment by Charles River Broadcasting Trust, established by Theodore Jones, to continue to air classical music in perpetuity, and it carried no non-classical music programs. However, the decision to interpret the commitment as a request rather than a demand resulted in the announced sale of the station to Greater Media on December 19, 2005. The trustees of the Charles River Broadcast Trust had already sold off portions of the trust’s property so that there was little physical property and real estate left. The AM transmitter site in Waltham was sold to a developer who built the Watermill Complex. This, and the sales of stations such as WCRQ in Providence, Rhode Island, marked the beginning of the gradual dissolution of the Theodore Jones trust. It was upon the death of Richard L. Kaye, an early manager, minority stockholder, and trusted associate of Jones, that the Charles River Trust would no longer maintain the commitments made by its founder.
Greater Media already owned five FM stations in the Boston market - the maximum allowed by the FCC - and one of Greater Media's Boston stations would have to be sold before the company could acquire WCRB. Speculation arose that Greater Media would sell off 99.5 WKLB-FM, as its Andover transmitter location provided poor overall coverage of the Boston market, in contrast to the company's other stations. These thoughts were confirmed on July 31, 2006, when Greater Media announced that it would sell the physical property of WKLB-FM and the intellectual property of WCRB to Nassau Broadcasting, thus saving the commercial classical format for the Boston area, albeit on a station with poorer coverage of Boston. At the same time, Greater Media announced that the country format and intellectual property of WKLB would relocate to the prime signal of 102.5 MHz. WCRB's transition from 102.5 to 99.5 was completed on Friday, December 1, 2006 at noon local time. The first selection broadcast on the new frequency was the Hallelujah Chorus from Handel's Messiah.
During the 1970s, 99.5 became WSSH (for "Wish 99.5"), which programmed a format of chiefly soft instrumental renditions of pop tunes with a few vocalists an hour, consisting of soft AC (adult contemporary) and standards cuts. In 1982 WSSH, evolved to a soft AC format gradually eliminating the instrumental renditions and became home to popular nighttime radio personality Delilah Rene before she became nationally syndicated. Ratings were very high through the 80's and WSSH often led other AC stations. By then, the station was separated from WLLH, but later gained a sister station on 1510 (now WWZN). WSSH had high ratings and was often the top rated adult contemporary radio station in the market throughout the 1980s.
However, in the early 1990s, ratings went from excellent to mediocre; part of the reason was the perception that WSSH was still an elevator music station. During this period, the station modified their soft AC format (by 1991), adding current product and some up-tempo AC tunes, evolving to a mainstream AC format. WSSH became the third place radio station, following WMJX and WVBF (now known as WROR, which subsequently became sister station to 99.5). In 1995, the owner of WSSH, Granum Communications, changed the format to smooth jazz, under the branding of WOAZ ("99.5 The Oasis"), mirroring Granum's KOAI in Dallas, Texas.
Then in 1997, Granum sold WOAZ and WBOS to Greater Media, which already owned WMJX, 96.9 WBCS (the incarnation of WKLB at that time) and 105.7 WROR (the former WVBF, and WCLB). On August 22, 1997, Greater Media swapped the frequencies of WOAZ and WCLB in a move where the format and personalities of WOAZ moved to 96.9 (adopting the call sign WSJZ), while WCLB moved to 99.5 and became "Country 99.5 WKLB", where it stayed until December 1, 2006. Greater Media noted that the move was made because the 99.5 signal is stronger than that of 96.9 in Essex County, home to many country music listeners.
The 99.5 station was spun off to Nassau Broadcasting Partners as a consequence of a deal where Greater Media acquired WCRB's current dial position, with 102.5 adopting the WKLB format and call sign. Nassau also acquired WCRB's call letters and programming. Nassau already has four classical-formatted stations in Maine which are affiliated with the World Classical Network. The two stations switched frequencies at noon on December 1, 2006. The last broadcast by WKLB on 99.5 was of the U.S. National Anthem. The first song played by WKLB at 102.5 was "Life Is A Highway" by Rascal Flatts. The last air personality on 99.5, and consequently the first live voice on 102.5, was longtime midday host Carolyn Kruse. A redesigned website was launched immediately after the frequency change.
Soon reports were coming to the station that showed the extent of the blackout. WCRB engineering checked the amount of diesel fuel remaining and found that it might not last more than a few hours. The fuel vendor was notified, but there was no fuel available. A radio engineer started driving around and discovered that the Civil Defense was trying to get a portable generator running that they had connected to the Waltham Hospital. The hospital had no power. The only generator available would not run. WCRB’s station engineer suggested that the electric company back-feed power from WCRB to the hospital, using the existing distribution lines, but disconnecting everybody else. The hospital was on Hope Avenue, off from South Street, on the other side of Brandeis University. This worked. WCRB fed power to the hospital and, incidentally, the fuel from the inoperative generator was transferred to WCRB’s tank. Within a few hours, WCRB had its fuel tank filled from donations. To have enough power available to feed the hospital, it became necessary to shut down the AM transmitter.