Ah yes. Grout. What every college music student has been studying Music History from for the last several decades. I remember my sister talking about snoozing thru her 8am Music History class back in the 1970s ;-).
My prof. used them for our course. We all showed up with different editions (purchased at used books stores and off the internet), and it was funny to see how they had changed details. I won a prize for my dramatic reading of the paragraph from my circa 1970 edition explaining why modern rock 'n' rollers just don't "get" Gregorian Chant, and why they ought to.