Charles H. Spurgeon on Psalms 33:2

Praise the Lord with harp. Men need all the help they can get to stir them up to praise. This is the lesson to be gathered from the use of musical instruments under the old dispensation. Israel was at school, and used childish things to help her to learn; but in these days, when Jesus gives us spiritual manhood, we can make melody without strings and pipes. We who do not believe these things to be expedient in worship, lest they should mar its simplicity, do not affirm them to be unlawful, and if any George Herbert or Martin Luther can worship God better by the aid of well tunes instruments, who shall gainsay their right? We do not need them, they would hinder than help our praise, but if others are otherwise minded, are they not living in gospel liberty? Sing unto him. This is the sweetest and best of music. No instrument like the human voice. As a help to singing the instrument is alone to be tolerated, for keys and strings do not praise the Lord. With the psaltery and an instrument of ten strings. The Lord must have a full octave, for all notes are his, and all music belongs to him. Where several pieces of music are mentioned, we are taught to praise God with all the powers which we possess.