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Of Music (1129. 1130).A drum with cogs working by wheels with springs .
A square drum of which the parchment may be drawn tight or slackened by the lever a b .
A drum for harmony .
 A clapper for harmony; that is, three clappers together.
 Just as one and the same drum makes a deep or acute sound according as the parchments are more or less tightened, so these parchments variously tightened on one and the same drum will make various sounds .
Keys narrow and close together; (bicchi) far apart; these will be right for the trumpet shown above.
a must enter in the place of the ordinary keys which have the ... in the openings of a flute.
281:629 : This chapter consists of explanations of the sketches shown on Pl. CXXI. Lines 1 and 2 of the text are to be seen at the top at the left hand side of the first sketch of a drum. Lines 3-5 refer to the sketch immediately below this. Line 6 is written as the side of the seventh sketch, and lines 7 and 8 at the side of the eighth. Lines 9-16 are at the bottom in the middle. The remainder of the text is at the side of the drawing at the bottom.