piano stool

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A round wooden stool used by piano players. It is less stable than the rectangular piano bench. The height can be adjusted by simply spinning the seat clockwise or counterclockwise, respectively.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a stool for piano players; usually adjustable in height