captain, instrument of musick, (great) lord, (great) measure, prince, three (from the margin)

“Captain” From Boyd’s Bible Dictionary:

(head). Title for a leader of a band of ten, fifty, hundred or thousand (Deut. 1:15; Josh. 10:24; Judg. 11:6,11). Also a civic meaning (Isa. 1:10; 3:3). “Captain of the Guard” (Acts 28:16), was commander of the Praetorian troop of Rome. “Captain of the Temple” (Acts 4:1), was chief of the Temple watchmen.

“Music” From Boyd’s Bible Dictionary:

(muse). Anciently known (Gen. 4:21; 31:27; Job 21:12). Vocal and instrumental, reached highest perfection in temple choirs (2 Sam. 6:5; 1 Chron. 25). Usual instruments, harp, timbrel, Psalter, trumpet, flute, pipe, and so forth.

“Captain” From Concise Bible Dictionary:

In the Old Testament this word is used for one filling any office of rule or command: as the head of a tribe (Num. 2:3-29); commander of an army, and so forth. The person who appeared to Joshua as “a man” declared himself to be “captain of the Lord’s host.” He told Joshua to remove his shoes from his feet, for the ground was holy, evincing that he was God’s representative to lead their warfare (Josh. 5:14-15). In the New Testament the Lord is called “Captain” of our salvation, ἀρχηγός, “chief leader” (Heb. 2:10).
There was also a “CAPTAIN OF THE TEMPLE,” στρατηγός (Luke 22:4, 52; Acts 4:1; Acts 5:24, 26). This word is literally “the leader of an army”; it is also applied to magistrates (Acts 16:20), but the captain of the temple was set not over the soldiers, but over the priests and Levites: (Compare Num. 32; 1 Chron. 9:11; Jer. 20:1).
THE CHIEF CAPTAIN or HIGH CAPTAIN is χιλίαρχος, lit. “Captain of a thousand,” applied to the chief of the soldiers in Jerusalem (Acts 21-25).
CAPTAIN OF THE GUARD (Acts 28:16), is στρατοπεδάρχης, properly “commander of a camp,” but here the prefect of the Prætorian Guard, an officer to whom state prisoners were entrusted at Rome.

“Music, Musicians, Musical Instruments” From Concise Bible Dictionary:

The harp and the organ, or pipe, were in use as early as Genesis 4:21. Laban, when chiding with Jacob for secretly leaving him, said he would have sent him away “with songs, with tabret, and with harp” (Gen. 31:27). The monuments show that the Egyptians had various musical instruments, the Israelites, therefore, if they had not known their use before going into Egypt, could have learned it there. When Moses sang the song of triumph at the Red Sea, Miriam answered with a tabret in her hand; and Samuel told Saul that he would meet a company of prophets with a psaltery, a tabret, a pipe, and a harp (1 Sam. 10:5).
There must have been with these prophets some knowledge of music, which doubtless under David was further cultivated and devoted to the service of God, their music being intimately connected with temple worship. He had several companies of singers, and players on instruments, which are often mentioned in the Psalm. As these were indited under the guidance of the Holy Spirit, we may conclude that this way of celebrating the praises of God was in accordance with the dispensation that then was. Such an exhortation as “Praise Him with the psaltery and harp,” is beautifully in place in the Psalms; but in the New Testament dispensation it is, “singing and making melody in your heart to the Lord”; and “I will sing with the spirit, and I will sing with the understanding also.” “They that worship Him must worship Him in spirit and in truth.”
In the headings of fifty-five of the Psalm the words occur, “To the chief musician”; the word is natsach, and simply means “to the chief or the leader,” and may therefore apply as much to the singers as to the musicians. The musical instruments are considered under their various names.

Strong’s Dictionary of Hebrew Words:

Transliteration:
shaliysh
Phonic:
shaw-leesh’
Meaning:
or shalowsh ( 1 Chron. 11:11; 12:18) {shaw- loshe'}; or shalosh (2 Sam. 23:13) {shaw-loshe'}; from 7969; a triple, i.e. (as a musical instrument) a triangle (or perhaps rather three-stringed lute); also (as an indefinite, great quantity) a three-fold measure (perhaps a treble ephah); also (as an officer) a general of the third rank (upward, i.e. the highest)
KJV Usage:
captain, instrument of musick, (great) lord, (great) measure, prince, three (from the margin)