Although he was more of a Country background, my favourite of the easy listening types was Charlie Rich, beautiful deep rich voice. I liked Mathis personally - as long as you didn't watch him singing. Always looked like he was in pain. Frankie Laine was a favourite too.
A little from col A, a little from col B. In truth, I got my knowledge of this through my Dad. He was a big fan of 50's type crooners - Sinatra, Matt Munro, Matthis, Andy William etc. My parents were publicans and a regular memory from late teens early twenties was coming back from a night out to find several regulars singing these songs round the bar. It's a better memory than it sounds! My Dad was not only a fan, he could sing these songs really well and at some points did so in the pub. Before I was born he made a few records and would also provide demo recordings for the likes of Cliff Richard etc.