Title A treatise of the natural grounds, and principles of harmony. / By William Holder ... To which is added, by way of appendix: Rules for playing a thorow-bass; with variety of proper lessons, fuges, and examples .. Also directions for tuning an harpsichord or spinnet. By the late Mr. Godfrey Keller ... The whole being revis'd, and corrected from many gross mistakes committed in the first publication of these rules.