The Dulcet Tones of the Fistula

Here is something I read in that book about the Middle Ages: "The king loved the dulcet tones of the fistula, a kind of pan-pipes; this was soon augmented by the powerful sound of a (water) organ." Ha ha! I thought it was kind of funny because I vaguely know the "fistula" as some kind of awful-sounding medical condition. Also, the cliche "dulcet tones" is kind of nice. And the unnecessary parentheses around "water" cap it all off for an enjoyable lark!