1 A song of ascents.
I
Out of the depths I call to you, LORD;

2 Lord, hear my cry!
   May your ears be attentive
   to my cry for mercy.

3 If you, LORD, keep account of sins,
   Lord, who can stand?

4 But with you is forgiveness
   and so you are revered.

II

5 I wait for the LORD,
   my soul waits
   and I hope for his word.

6 My soul looks for the Lord
   more than sentinels for daybreak.d
   More than sentinels for daybreak,

7 let Israel hope in the LORD,
   For with the LORD is mercy,
   with him is plenteous redemption,

8 And he will redeem Israel
   from all its sins.

In deep sorrow the psalmist cries to God. Deep anguish makes the psalmist feel “like those descending to the pit.” (Psalm 130:1–2)

He asks for mercy for the sins committed. The experience of God’s mercy leads one to a greater sense of God. (Psalm 130:3–4).

The psalmist’s trust ((Psalm 130:5–6) becomes a model for the people ((Psalm 130:7–8).

This is the Latin version of the Septuagint text:
[Canticum graduum]
De profundis clamavi ad te, Domine;

Domine, exaudi vocem meam.
Fiant aures tuæ intendentes
in vocem deprecationis meæ.

Si iniquitates observaveris, Domine,
Domine, quis sustinebit?

Quia apud te propitiatio est;
et propter legem tuam sustinui te, Domine.

Sustinuit anima mea in verbo ejus:
Speravit anima mea in Domino.
A custodia matutina usque ad noctem,

speret Israël in Domino.
Quia apud Dominum misericordia,
et copiosa apud eum redemptio.

Et ipse redimet Israël
ex omnibus iniquitatibus ejus.

I searched for a listenable video clip of De Profundis. A few days ago a video clip 5′ 5” long on YouTube titled “De Profundis (Septuagesima Sunday, Tract)” uploaded by SGeorgeAZ on Jul 13, 2011 impressed me.

This video in addition to the music has Gregorian chant notation from the Liber Usualis (1961), p. 499 and Latin lyrics sung by the Benedictine Monks of Santo Domingo de Silos.