From BiblePortal Wikipedia

Smith's Bible Dictionary [1]

Psaltery. This was a stringed instrument of music to accompany the voice. The Hebrew, nabel or nebel is so rendered, in the Authorized Version, in all passages where if occurs, except in  Isaiah 5:12;  Isaiah 14:11;  Isaiah 22:24, marg.;  Amos 5:23;  Amos 6:6, where it is translated Viol . The ancient viol was a six-stringed guitar. In the Prayer Book version of the Psalms, the Hebrew word is rendered "lute."

This instrument resembled the guitar, but was superior in tone, being larger, and having a convex back, somewhat like the vertical section of a gourd, or more nearly resembling that of a pear. These three instruments, the psaltery or sautry, the viol and lute, are frequently associated in the old English poets and were clearly instruments resembling each other though still different. The Greek psalterium ( psalterion ), from which our word is derived, denotes an instrument played with the fingers instead of a plectrum or quill, the verb being used of twanging the bow-string.

It is impossible to say positively with what instrument the nebel of the Hebrew exactly corresponded, From the fact that nebel in Hebrew also signifies a wine-bottle or skin, it has been conjectured that the term, when applied to a musical instrument, denotes a kind of bagpipe. The psalteries of David were made of cypress,  2 Samuel 6:5, those of Solomon of algum or almug trees.  2 Chronicles 9:11. Among the instruments of the band, which played before Nebuchadnezzar's golden image on the plains of Dura, we again meet with the psaltery.  Daniel 3:6;  Daniel 3:10;  Daniel 3:15, Chaldaic, pesanterin .

Morrish Bible Dictionary [2]

The principal word used is nebel, and it is supposed to refer to some unknown form of stringed instrument used to accompany the voice. It is at times mentioned along with the harp.  1 Samuel 10:5;  Psalm 33:2;  Psalm 144:9;  Psalm 150:3; etc. The same word is also translated VIOL in  Isaiah 5:12;  Isaiah 14:11;  Amos 5:23;  Amos 6:5 . In  Daniel 3:5-15 the word is pesanterin.

Fausset's Bible Dictionary [3]

A stringed instrument played by the hand to accompany the voice, Hebrew Nebel . In  Psalms 33:2 omit "and," translated "sing with the psaltery an instrument of ten strings." Josephus (Ant. 7:12, sec. 3) mentions that ordinarily it had 12 strings; Nebel means literally, a leather bottle, the psaltery was named so from its shape ( Psalms 92:3;  Psalms 144:9). The king, or, "lyre," had ten strings, but was played with a quill, not with the hand.

King James Dictionary [4]

PSAL'TERY, n. Gr. An instrument of music used by the Hebrews,the form of which is not now known. That which is now used is a flat instrument in form of a trapezium or triangle truncated at the top, strung with thirteen chords of wire, mounted on two bridges at the sides, and struck with a plectrum or crooked stick.

Praise the Lord with harp sing to him with the psaltery, and an instrument of ten strings.  Psalms 33

Easton's Bible Dictionary [5]

 Isaiah 5:12  Daniel 3:5,7,10,15

Webster's Dictionary [6]

(n.) A stringed instrument of music used by the Hebrews, the form of which is not known.

Hastings' Dictionary of the Bible [7]

Psaltery . See Music, etc., § 4 .

Watson's Biblical & Theological Dictionary [8]

See Music .

American Tract Society Bible Dictionary [9]

See HARP, and MUSIC.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [10]

Bibliography Information McClintock, John. Strong, James. Entry for 'Psaltery'. Cyclopedia of Biblical, Theological and Ecclesiastical Literature. Harper & Brothers. New York. 1870.

Kitto's Popular Cyclopedia of Biblial Literature [11]