Your observation only reinforces my disdain for every episode produced after the 7th season. Yeah, they label them "Columbo", but as far as I'm concerned, they represent nothing more than a romper room for aging has-beens.
In fact, there are even a few eps in seasons six and seven that don't count in my book either, but thankfully, the force of nature will prevent them from adding another shameless example to the list.
I am amazed at how often we get this question, both by email and here on the forum -- clearly, a lot of people like that song. Unfortunately, I have no idea of the answer. "Columbo" never had musical credits for the singers of background music, so the performers will probably be forever anonymous.