Holiday Inn Nighttime with "Dolly Holiday" came later -1966 to 1973. Quite successful for several years. Provided the commentary but then the stations would have to supply the LP cuts indicated.Except for a couple of stations like WPAT in the New York market and KPOL in LA, I can't see many true "Beautiful Music" stations that endured into the 70s. And those two I mention had FM simulcasts that were listed in combined form in Arbitron... generally as the AM station.
Some, like "Ocean" in Miami, left the format in the earlier 70's. And even ones like WVCG-1070 in Miami had their FM as well.
In the 1976 Duncan book, I can not find a single stand-alone AM Beautiful Music station with significan ratings.
But format radio pretty much started taking over in the early 50's when Top 40 was created. By the middle of the decade, there were few block programmed stations and those were, musically, MOR in that era.
Most of those, if they played instrumentals, used a big percentage of bands and not so much Jackie Gleason and the more modern "studio orchestra" sound.
You are missing the fact that Top 40 was created in 1951, and it played "the hits". When rock 'n' roll hits came along, the stations played both traditional sounds and the newer artists together... even as late as 1960 when many stations celebrated "Volare" as the prior year's #1 song... a definite MOR tune!
The stations that were not Top 40 were generally among just a couple of big formats by the end of the 1950's: country, "race music" (sorry, but that is how it was called), and some form of MOR, often called "Full Service". Few were all instrumental. The MORs were the most varied, as they might play some instrumentals, be more traditional or even play some of the crossover artists that had Top 40 hits, like Nat "King" Cole and even Paul Anka
I was an AM band DXer starting in 1958 and in the next 5 or so years logged about 2,500 stations. I can recall very few that played instrumentals in rated dayparts, although there were several shows, such as the Holiday Inn overnight show that played instrumentals.
There were exceptions, such as McLendon's 1960 launch of KABL 960 in San Francisco... a station that took advantage of poor FM coverage in that market. KABL got a few imitators, but the format was not that common on AM
In 1950 there were about 1000 licensed FMs in construction or on the air. By 1960 they had fallen to just over 600. The independent FM for the most part had closed. The others simulcast their AM. Then, in the ealy 60's a new set of owners filed for FMs and got them and stuck with it.
And was not into effect until the start of 1967.
Major market AM station owners, faced with non-duplication rules, looked for the formats that would least affect their cash cows, and so Beautiful Music and Album Rock seemed to be the best way to protect their AMs.
But if anything made Beautiful Music so successful, it was the duo of Shulke and Taylor who used syndication to mae doing the format cheap and easy: no cost of building a library, no PD, generally no talent, ability to automate, and even help in promotion and sales.
I would respectfully dispute the statement that there were few Beautiful Music AMs.
Schulke's SRP and Taylor's Bonneville Program Services got top dollar. SRP was when introduced in 1969 two and a half to three and a half times more costly than other Beautiful syndicators. Plus Schulke often would not service them unless they spent the dollars to upgrade their automation and technical systems meet his specifications. Wanted his clients to put out the best signal in their markets as well as take a highly-disciplined approach to what they were doing. In fact the FCC investigated him because of the demands he made on his clients. They construed them as infringing upon the rights of stations to do as they please in servicing the public.


