With Psalm 150, the fifth and final concluding Hallelujah Psalm, we come to the end of the book of Psalms. As in Psalm 148, the word "praise" (hallel) is used here 13 times. Yet this psalm more closely follows the pattern of only the first part of Psalm 148. In this case we see, within the framing Hallelujahs at the beginning and end, 10 imperative calls to praise God (Psalms 150:1-5 Psalms 150:1-5  Praise you the LORD. Praise God in his sanctuary: praise him in the firmament of his power.
 Praise him for his mighty acts: praise him according to his excellent greatness.
 Praise him with the sound of the trumpet: praise him with the psaltery and harp.
 Praise him with the tambourine and dance: praise him with stringed instruments and organs.
 Praise him on the loud cymbals: praise him on the high sounding cymbals.
American King James Version×) followed by a single summary call to praise in the jussive subjunctive mood--that is, in the form of "let them" (see verse 6). As these calls are brief and without expressive praise, the entire psalm has the form of an extended doxology (a doxology being a brief expression of praise). Recall that Books I through IV of the Psalter each end with a short doxology evidently added to the last psalm in each book (see Psalms 41:13 Psalms 41:13Blessed be the LORD God of Israel from everlasting, and to everlasting. Amen, and Amen.
American King James Version×; Psalms 72:18-19 Psalms 72:18-19  Blessed be the LORD God, the God of Israel, who only does wondrous things.  And blessed be his glorious name for ever: and let the whole earth be filled with his glory; Amen, and Amen.
American King James Version×; Psalms 89:52 Psalms 89:52Blessed be the LORD for ever more. Amen, and Amen.
American King James Version×; Psalms 106:48 Psalms 106:48Blessed be the LORD God of Israel from everlasting to everlasting: and let all the people say, Amen. Praise you the LORD.
American King James Version×). Now at the end of Book V, the entirety of Psalm 150 appears to perform the same function--and it may have been composed specifically to close the Psalter.
Though brief, Psalm 150 encompasses many elements of the book of Psalms. As the Zondervan NIV Study Bible comments in its introductory note on the song, "This final call to praise moves powerfully by stages from place [verse 1] to themes [verse 2] to orchestra [verses 3-4] to choir [verse 6], framed with Hallelujahs."
Verse 1 tells us where God should be praised--in His sanctuary and in His mighty firmament. The sanctuary is God's temple, meaning His physical temple in Jerusalem and also His spiritual temple on earth, His Church, as well as His heavenly temple. The "firmament" here signifies heaven or the sky (see Genesis 1:6-8 Genesis 1:6-8  And God said, Let there be a firmament in the middle of the waters, and let it divide the waters from the waters.
 And God made the firmament, and divided the waters which were under the firmament from the waters which were above the firmament: and it was so.
 And God called the firmament Heaven. And the evening and the morning were the second day.
American King James Version×), and the meaning in this case is probably the entire, vast universe.
Verse 2 of Psalm 150 tells us why God should be praised--"for His mighty acts" (for what He does) and "for His excellent greatness" (for who and what He is).
Verses 3-5 tell us "how God should be praised--with the whole orchestra (eight instruments: wind, string, percussion), with dancing aptly placed at the middle" (Zondervan,note on verses 3-5)--recalling the celebratory elements of the previous psalm (compare Psalms 149:3 Psalms 149:3Let them praise his name in the dance: let them sing praises to him with the tambourine and harp.
American King James Version×). Perhaps the idea here is simply to joyfully praise God with whatever we have to praise Him.
And finally, verse 6 of Psalm 150 tells us who should praise God--the choir of all that have life and breath. As The Nelson Study Bible remarks on this verse: "The very breath that God gives us should be used to praise Him. As long as we live we should praise our Creator (Psalms 146:1 Psalms 146:1Praise you the LORD. Praise the LORD, O my soul.
American King James Version×, 2). By His breath God created all things (Psalms 33:6 Psalms 33:6By the word of the LORD were the heavens made; and all the host of them by the breath of his mouth.
American King James Version×), and by our breath we should adore Him. The Book of Psalms begins with God's blessing on the righteous (Psalms 1:1 Psalms 1:1Blessed is the man that walks not in the counsel of the ungodly, nor stands in the way of sinners, nor sits in the seat of the scornful.
American King James Version×) and concludes with all of creation blessing its loving Creator."
In all that we think, in all that we say, in all that we do, let it be to the praise of our great and loving God, our Almighty Maker and Savior and King, the infinite and majestic Lord of all creation. And let us all sing with joyful hearts, Hallelujah! Praise the Lord.