Robert Guthrie Testimony: “Guitarists who love the beauty of the traditional Spanish guitar sound will find in Joseph Slack’s instruments the ideal combination of qualities: refinement of tone, powerful rapid response, and playability. Over the last two months, I played a number of guitars by some of the finest and most respected Spanish builders of the last 50 years, all excellent concert instruments by any standards.  At the end of this period I chose to purchase one of Mr. Slack’s guitars because I preferred the sound. Players will immediately notice the innate musicality of his guitars. The blending of harmonies and the ability to control timbre is outstanding. Although I would call the overall tone of his instruments sweet, there is plenty of power available, and to my mind one of the most beautiful
rasgueado  sounds I have heard.