I have right here a little booklet called "How to Vamp Without Music", which tells you how to play chords without using any conventional staff notation. 16 pages, no author named, published by John E. Dallas & Sons, Dallas Building, Clifton Street, London E.C.2, price 1/- (which dates it before 1971?). Tune examples: No Place Like Home, Cementine, John Brown's Body, Blow the Man Down, Annie Laurie. The chordings are pretty normal.