A brief introduction to the skill of musick [electronic resource] : in three books : the first, The grounds and rules of musick, according to the ga-mut and other principles thereof : the second, Instructions for the bass-viol, and also for the treble-violin, with lessons for beginners / by John Playford ... ; the third, The art of descant, or, Composing musick in parts, by Dr. Tho. Campion, with annotations thereon by Mr. Chr. Simpson