As an organist I frequently compose psalm-settings for weekend Masses. I have never once come across a situation where I have had to alter the words - remembering that I’m setting music for the words and not words for the music is helpful & I find it easier to write a melody line which suits the tone of the text. I think the key is to keep it simple. Create a simple response which the congregation will be able to sing and use a psalm-tone for the verses. Certain translations are easier to set to a psalm-tone - missalettes in Ireland generally use the Grail Translation and they work well. Sometimes the tone you would like to use will not suit the words in one particular line of a verse - for example, in a line which expresses sorrow, sadness, anger, etc., it may seem unnatural and unsuitable to move up to a higher note as this is more often a way of expressing joy and happiness. If this is the case, there is no need to change the words in my opinion - change your psalm tone slightly instead (for all verses or just the strange one).
I understand that some common hymns such as “Eagles Wings” and “The Lord’s my Shepherd” have altered the standard wording used in missalettes - I don’t expect that there is a problem with this. I see the problem being with the fact that they are not responsorial psalms - key word being responsorial. If they do not give the congregation a chance to respond to the psalm with an acclamation then the music is not really serving its purpose at that particular point in the Mass. As pnewton said, I think the best solution is for the organist or a choir member to compose the psalm using the missalette - if it is kept simple it will not take much time, and of course the upside of using psalm-tones is that they can frequently be recycled throughout the year!
NPC, I agree with you!
I have done the same thing as NPC - composed music to go with the words of the psalm (not the other way around).
The psalms were composed to be the songs used in the liturgical worship of the ancient Israelites, and as such by their very nature should always be sung. Times when I have been faced with a Sunday psalm in the missalettes with either a dreadful, nearly unsingable, or just plain ugly melody, I have written my own music to go with it.
I never take the chicken’s way out - using another psalm (which is also *not allowed *).
Times when the psalm is the body of a song, such as
On Eagles Wings, or one of the many beautiful settings of the 23rd Psalm for example, but when the song is not
responsorial in nature and thus not appropriate to be used as a Responsorial Psalm, I will try to use the song in another part of the Mass (say, as a Communion song), the theory being to reinforce the message in the minds of the congregation. (Usually, by Communion time, half of the congregation can’t remember the Psalm, the readings, the Gospel or the homily.

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When I attended the New York School of Liturgical Music, we were taught that it was okay to play around a little with the words of the psalm in order to make it more singable. I have always found it frustrating, however, that no one ever really defined how much “playing around” is licit. A word or two? A whole line? I’d rather use the words as they appear in the Lectionary, then I know I’m safe.
