The English word minstrel is derived from the Latin word ministrellus which meant someone who served others ("minister," which is also derived from the same word, also simply means servant - see the Fact Finder question below) by means of their making music or some other entertaining performance. Although now generally defined as "a singer of folk songs," minstrel is used, only twice, by some English-language Bible translations for either, in the Old Testament, a player on a stringed instrument (who could also have been singing) or, in the New Testament, a flute player (who could obviously not also have been singing). The Old Testament Hebrew word is pronounced naw-gan, and literally means to play, and sing along with, a stringed instrument. The New Testament Greek word is pronounced ow-lay-tace, and literally means to play the flute.
"And it came to pass, when the minstrel played, that the hand of The Lord came upon him"
In the Old Testament, "minstrel" is used for the player of a stringed instrument that played while the prophet Elisha, who at first assisted, and later succeeded Elijah after Elijah's retirement (see Where Did Elijah Go?), proclaimed a miraculous sign:
"And Elisha said, As The Lord of hosts liveth, before whom I stand, surely, were it not that I regard the presence of Jehoshaphat the king of Judah [see Kings of Israel and Judah], I would not look toward thee, nor see thee. But now bring me a minstrel."
"And it came to pass, when the minstrel played, that the hand of The Lord came upon him. And he said, Thus saith The Lord, Make this valley full of ditches. For thus saith The Lord, Ye shall not see wind, neither shall ye see rain; yet that valley shall be filled with water, that ye may drink, both ye, and your cattle, and your beasts. And this is but a light thing in the sight of The Lord: he will deliver the Moabites also into your hand. And ye shall smite every fenced city, and every choice city, and shall fell every good tree, and stop all wells of water, and mar every good piece of land with stones."
"And it came to pass in the morning, when the meat offering was offered, that, behold, there came water by the way of Edom, and the country was filled with water."
"And when all the Moabites heard that the kings were come up to fight against them, they gathered all that were able to put on armour, and upward, and stood in the border. And they rose up early in the morning, and the sun shone upon the water, and the Moabites saw the water on the other side as red as blood: And they said, This is blood: the kings are surely slain, and they have smitten one another: now therefore, Moab, to the spoil. And when they came to the camp of Israel, the Israelites rose up and smote the Moabites, so that they fled before them: but they went forward smiting the Moabites, even in their country." (2 Kings 3:10-24 KJV)
In the New Testament, "minstrel" is used to refer to flute players who played as part of a mourning ritual for a girl who had just died. Their "tune" no doubt changed when Jesus Christ restored her to physical life:
"While He spake these things unto them, behold, there came a certain ruler, and worshipped Him, saying, My daughter is even now dead: but come and lay thy hand upon her, and she shall live. And Jesus arose, and followed him, and so did His disciples." (Matthew 9:18-19 KJV)
"And when Jesus came into the ruler's house, and saw the minstrels and the people making a noise, He said unto them, Give place: for the maid is not dead, but sleepeth. And they laughed Him to scorn. But when the people were put forth, He went in, and took her by the hand, and the maid arose. And the fame hereof went abroad into all that land." (Matthew 9:23-26 KJV)
Fact Finder: Why are the servants of God, who are sent to serve God's people, called "ministers" - which merely means servant?