This exhortation is not referring to public worship, but to daily conversation and even to solitary activity--"speaking to yourselves" and "making melody in your heart to the Lord" (Ephesians 5:19).

Source:

KJV Defenders Study Bible, by Dr. Henry Morris, Ph.D.
Publisher: Thomas Nelson
Language: English
DEF 10 ISBN 0-529-10444-x
DEF 10-1 ISBN 0-529-10445-8