《晋书·志·第六章》
假使声调低的人用三尺二的笛，则称之为三尺二调；声调高的人用二尺九的笛，则称之为二尺九调。
假令声浊者用三尺二笛，因名曰此三尺二调也；声清者用二尺九笛，因名曰此二尺九调也。
If someone with a low pitch uses a flute of three feet and two inches, it is called a three-foot and two-inch pitch; if someone with a high pitch uses a flute of two feet and nine inches, it is called a two-foot and nine-inch pitch.