Robert L. Marshall Eighteenth Century Keyboard Music — "Engramelle introduces a large numbers of ratios to represent uneven notes (such as 2:2, 3:1, 3:2 and even 7:5), but he ultimately concedes that his mathematical and mechanical constructs at best can only approximate the subtleties of the art"
Ploger, Marianne; Keith Hill (2005). Craft of Musical Communication. Archived from the original on 21 January 2013. Retrieved 1 December 2015., from Johnson, Cleveland (2006). Orphei Organi Antiqui: Essays in Honor of Harald Vogel. Orcas, WA: Westfield Center. ISBN097784000X.
Ploger, Marianne; Keith Hill (2005). Craft of Musical Communication. Archived from the original on 21 January 2013. Retrieved 1 December 2015., from Johnson, Cleveland (2006). Orphei Organi Antiqui: Essays in Honor of Harald Vogel. Orcas, WA: Westfield Center. ISBN097784000X.
