Under-board sb.

[UNDER-¹ 5 b and UNDER a. 1 b.] The lower of two boards forming an organ bellows or wind-chest.

1

1781. Encycl. Brit. (ed. 2), VIII. 5747/1. [In] the church-organ … the sound-board … is composed of two parts, the upper board … and the under board.

2

1845. Stimpson, Gt. Organ B’ham, 8. Directly over the under-board is situated the upper-board, which is perforated with holes to correspond with those in the under-board.

3