Pepys remarks in his diary on going to the coffee house to play music with his mates. He played recorder and comments on the company of John Blow, Daniel and Henry Purcell et al. The suggestion is that he is going to a recognisably modern 'session'. My researches on the community of muisicians known as the 'Blind Fiddlers of Sheffield' (despite their playing flutes, singing etc.) also show that the practice was prevalent in the late 18th and early 19th centuries. My considered opinion is that the 'session' has been with us for a hell of a long time!