Sheminith

Boyd’s Bible Dictionary:

(eighth). A musical term, variously surmised to mean the instrument, one of eight strings, the octave, the time of the piece, the part, air, pitch, or key (1 Chron. 15:2121And Mattithiah, and Elipheleh, and Mikneiah, and Obed-edom, and Jeiel, and Azaziah, with harps on the Sheminith to excel. (1 Chronicles 15:21); Psa. 6; 12 titles).

Concise Bible Dictionary:

A Hebrew word in the headings of Psalm 6 and Psalm 12, and in 1 Chronicles 15:2121And Mattithiah, and Elipheleh, and Mikneiah, and Obed-edom, and Jeiel, and Azaziah, with harps on the Sheminith to excel. (1 Chronicles 15:21). It will be seen that in the margin these passages read “on the eighth,” with which the LXX agrees. It was probably an instrument of eight strings (from shemoneh, “eight”). Gesenius says it means “octave;” hence the lowest notes of the scale, and sung by men.

Strong’s Dictionary of Hebrew Words:

Number:
8067 (find all occurrences in KJV Bible)
Transliteration:
shmiyniyth
Phonic:
shem-ee-neeth’
Meaning:
feminine of 8066; probably an eight-stringed lyre
KJV Usage:
Sheminith

Jackson’s Dictionary of Scripture Proper Names:

the eighth

Potts’ Bible Proper Names:

To excel; to oversee; the eighth; octave:―an eight-stringed lyre, 1 Chron. 15:21. {Excellere}