When Beautiful Music hit its stride... very early 70's... until its decline after about 1985, the format was generally quarter hour sets with two instrumentals, one vocal, and one to two more instrumentals (depending on length).
Some syndicators were a bit more conservative, keeping some instrumental versions of "standards" and show tunes in the format, but in most cases the songs were contemporary. By the mid-70's, the major syndicators were recording custom instrumental covers of Top 40 and AC songs in Europe and supplementing with the most modern sounding album releases... Mauriat, Caravelli, James Last, Richard Clayderman, Jean-Claude Borelli, Francis Goya, Norrie Paramour, etc.
The vocals tended to be either MOR songs or acceptable AC songs and even some Top 40 ballads on occasion. In the vocals, the sound had to be very contemporary... Streisand, not Sinatra. Singers, not crooners. And Beautiful Music had some of its own hits, like the Roger Whittaker "Last Farewell" that was on every Beautiful Music station from Anchorage to Asunción.
I was a member of the "alliance" of independent Beautiful Music stations / syndicators that included Kala Music, WDVR, EZ Communications and others and we recorded hundreds and hundreds of custom cuts, mostly in England, covering current songs or Top 40 material that we thought did not have a good Beautiful Music version on commercial releases. I also recorded in Madrid additional material for the Latin American market which was entirely covers of late-60's to present pop hits.
The major fall-off in Beautiful Music stations did not happen until the period beginning around 1985 and beyond. Some stations morphed into AC, others just changed format totally.
I did not say that the Ventures were part of Beautiful Music. I said that many pre-boomers and the first decade or so of Baby Boomers grew up when Top 40 radio played many instrumentals so non-vocal music was part of those listeners' experience. The transition into 80% instrumental Beautiful Music listening was not hard, as instrumentals... including soft ones like "Love is Blue" and "Theme from a Summer Place" were very much part of the Top 40 experience then.
And... since much of a Beautiful Music station's playlist was made up of instrumental versions of songs like "Blue Velvet" and "Put Your Head on my Shoulder" the sound was familiar and pleasant.