In times past, some editions of the 1650 Scottish Metrical Psalter were specially prepared to include notes or annotations from notable commentators on the Psalms to help Christians follow the precept articulated in 1 Cor. 14.15 and also found in the Westminster Directory for Public Worship that one must "sing with understanding" when singing the Psalms of David.
I am aware of five such versions (there might be more) that have been published over the centuries. One includes the notes on the Psalms by David Dickson, a 17th century Scottish Presbyterian divine. Another includes the comments of Matthew Henry, an English Presbyterian divine who lived in the 17th and 18th centuries. John Brown of Haddington, an 18th century Scottish Presbyterian, published his notes on the Psalms in metre which are still available today. There is a 19th century edition of the Scottish Metrical Psalter with the notes of Matthew Henry and John Brown combined. And another 19th century edition includes the notes of William King Tweedie, Scottish Presbyterian, which was published by the General Assembly of the Church of Scotland soon after his death.
If one has Matthew Henry's famous commentary on the Bible, it is a useful exercise to pay particular heed to his directions (found in his annotations on each psalm) on how to rightly sing that psalm. His comments provide not only sound exegesis, but helpful application for the psalm-singer.
Each of these resources is helpful for the pastor or head of household in leading those under his charge in the singing of psalms, as well as for use in private devotions. I commend them all highly.