"Sing Hallelujah to the Lord" was a popular worship song written in 1974 by Linda Stasson.  She wrote it for a music composition class at Calvary Chapel in Costa Mesa, California.

The word "hallelujah" is a command to praise the Lord, and we see it often in the book of Psalms.  Some of these psalms were used for Jewish festivals, and they would begin and end with "hallelujah."  Psalm 150, the closing psalm in the book of Psalms ends with "Let everything that hath breath praise the Lord.  Praise ye the Lord."  (Hallelujah).

The Hebrew "hallelujah" was slightly altered to "Alleluia" in the New Testament Greek.  Revelation 19:1 says, "And after these things, I heard a great voice of much people in heaven, saying, "Alleluia; Salvation and glory and honor, and power unto the Lord our God."

The words are:

Sing hallelujah to the Lord,

Sing hallelujah to the Lord.

Sing hallelujah, sing hallelujah,

Sing hallelujah to the Lord.

Sometimes, people add verses, such as "Christ is risen from the dead."  It is a good chorus for transitioning to worship.