quite simply, this is a term used to describe former Roxy Music frontman Bryan Ferry. His vocal crooning styles, his habit of wearing stylish clothes when he plays the piano, synthesizer, and occasionally guitar, his stylish, suave, sophisticated and elegant image that he shows in pictures, performance and video and the fact that Roxy Music inspired punk rock and New Wave leads to this designation. Today he pursues his solo career, sometimes covering artists that inspire him - like Elvis Presley, Bob Dylan, Marvin Gaye and yes, Frank Sinatra. His sound is now generally the New Romantic and Eurodisco styles that Roxy Music laid the foundation for.
I heard Roxy Music on the radio and saw some of their videos (as well as Bryan Ferry solo)on MTV in the Eighties. In 1990 I had a buyer's card filled up with purchase punches which meant I could get a free album. The girl at the checkout said that the album I got (a Roxy best-of) was really good, and she said that Bryan Ferry is a "punk Sinatra". Man was she right! I've been a fan ever since.