Well, I went browsing as mentioned, and picked a good time too; the guys at the record shop were getting ready to discard several boxfuls of easy listening (they buy collections and pretty much anything that isn't 60's rock gets dumped.) Picked out for free several LPS containing versions of "Cuando Calienta;" have checked them out, and Billy Vaughn's 1963 version is pretty darn good.
I've often wondered if traditional easy-listening might have lasted longer had there been instrumental versions of some of the softer rock songs that were arranged to sound as much as possible like the originals, but with an instrument or a section in place of the vocal. In the 60's, this could have been done with, say, Bobby Vinton or Petula Clark; or in the 70's with Neil Diamond, Cher, or John Denver. All of these singers and others worked with terrific arrangers; and instrumentals with the same "feeling" might have had a lot of potential. Maybe sounds like instrumental karaoke, but it could have added some punch to the format while staying true to its nature.