Since there is so much discussion about worship and worship music, I thought that the following principles and guidelines for selecting music for the church would be very helpful. It was written by our federation of churches back in our Synod 2004. Those who use CCM please specially note Guidelines 7, 10 and 11.
Principles & Guidelines for Selecting Music in the Church by the United Reformed Churches in North America
The song of the church is to be suitable for the church‘s worship to the glory of God!
1. The songs of the Church are to be Scriptural.
In content, form, and spirit the Church‘s songs must express the truth of the Holy Scriptures.
Augustine, referring to the singing of Psalms, said,
No one can sing anything worthy of God which he has not received from Him. . . then we are assured that God puts the words in our mouth.
2. The songs of the Church are to be a sacrifice of praise. 
Singing is an important element of the congregation‘s response to God‘s redeeming work in Christ Jesus and the Word proclaimed in the worship service.
John Calvin wrote,
Singing has great strength and power to move and to set on fire the hearts of men that they may call upon God and praise Him with a more vehement and more ardent zeal. This singing should not be light or frivolous, but it ought to have weight and majesty.
3. The songs of the Church are to be aesthetically pleasing.
The songs for worship are to be a beautiful blend of God-honoring poetry and music.
About such beauty, Abraham Kuyper remarks:
The world of sounds, the world of forms, the world of tints, and the world of poetic ideas, can have no other source than God; and it is our privilege as bearers of His image, to have a perception of their beautiful world, artistically to reproduce, and humanly to enjoy it.
GUIDELINES FOR SELECTING SONGS:
1. The songs of the Church must be thoroughly biblical. They are to represent the full range of the revelation of God, Father, Son and Holy Spirit.
2. The Book of Psalms is foundational for the Church‘s songs. Therefore, all of these Psalms, in their entirety, ought to be included in the Church‘s songbook.
3. When Psalms or other portions of Scripture are set to music, the words must be faithful to the content and form of the inspired text.
4. In the case of songs other than the versification of Scripture, the words must faithfully express the teaching of Scripture as summarized by our Reformed confessions.
6. The songs of the Church must reflect and preserve the language of the Church of all ages rather than accommodating current secular trends.
7. In content and form, the songs of the Church must be free from artificiality, sentimentality, and individualism.
8. The music of the song should suit the text.
9. The music of the Church should be expressive of the Reformed tradition. Use is to be made of the music developed in the tradition of this rich heritage.
10. The music of the Church should not be borrowed from music that suggests places and occasions other than the Church and the worship of God.
11. The melodies and harmonies of church music must be suitable for congregational singing, avoiding complicated rhythms, excessive syncopation, and a wide range of pitch.