As given in number 139 of the Rite of Penance, Psalm 51 is presented almost in its entirety. Thirteen and a half verses are organized into seven stanzas–more text than you’ll find in any responsorial psalm in the Missal. Did those who composed this rite intend this? When do you think an extended musical version of Psalm 51 would be good liturgy? What about this famous setting?
My own sense is that a musical setting of Psalm 51 could well extend into several minutes and involve a more complex dialogue of assembly, soloists, choir, and possibly other narrative forms.
Back to what is given. “Miserere mei …” is not the antiphon, but this:
Give me back the joy of your salvation.
But the core of Psalm 51 contains two other verses more well known as Roman Rite antiphons. Verse 9 is used for the Rite of Sprinkling:
Cleanse me of sin with hyssop, that I may be purified;
Wash me, and I shall be whiter than snow.
This verse is linked with the following four lines in the longest stanza:
Let me hear the sounds of joy and gladness;
the bones you have crushed shall rejoice.
Turn away your face from my sins,
and blot out all my guilt.
It’s interesting that the framing of stanzas in the Lectionary rather ignore the natural break in the composition between verses 10 and 11. That latter verse begins a poetic echo of verses 3-4: the penitent is calling on God’s mercy again. “Blot … my guilt” parallels the “wipe … my offense” of verse 3.
And we are most familiar with the psalmist’s prayer for a clean heart, and the call of the psalmist for the Spirit of God to sustain a hoped-for virtue:
A clean heart create for me, O God,
and a steadfast spirit renew within me.
Cast me not out from your presence,
and your Holy Spirit take not from me.
My sense is that one can take individual verses out of this psalm for personal benefit. Indeed, it is difficult to find a line or two insufficient as a penitential mantra. The entire composition may be unparalleled in the Psalter as a prayer for mercy. From great sin, God clearly works great grace. That should be a comfort to any sinner.