What is the difference…

Tad, don't take it personally. It is the nature of an Internet discussion board. Some topics will grab someone's attention, others (that seem important to the original poster) don't get a second post. It happens, but is not anything against you.

MP

 

Most well-received commentators acknowledge that psalms, hymns and spiritual songs were distinctive styles. Exactly what the difference between them was, is not known.

Psalms are hymns of the Jews, the Book of Psalms. They were called psalms after the psaltery, a harp-like instrument employed by the Jews.

Hymn is a Greek word meaning song of praise. Hymns were generally solemn as opposed to paeans which were exultant and fervent, and dithyrambs which were wildly exuberant.

Spiritual songs are songs of any arrangement that don't elicit any mood or emotion inconsistent with Christian character.

 

We're speaking of styles, not content, and so was Paul. Paul didn't have to say, "Hymns to God the Father," because the Ephesians and Colossians were rational enough to understand that He wasn't endorsing hymns to Apollo or Zeus.

So when Paul said "spiritual songs," the content was already understood. He was specifying the manner, style, decorum, etc. of our interaction when speaking of Christ and the Gospel. He contrasts it with the excesses sought by the world.