The ninth psalm is the start of the disconnect in psalm numbering between Septuagint or Vulgate and the modern psalter. The split runs through to the last three psalms which, like the first eight, are in sync again. Why bother? Many musical sources quote the earlier numbers widely used by composers in days gone by. It can be confusing.
In the early Septuagint translation and the original Hebrew, Psalms 9 and 10 were one song. Isaac Everett says:
It’s clear that they form a single unit because the combined text is acrostic, with the first letter of each forming the Hebrew alphabet: Psalm 9 is roughly A-K and Psalm 10 is roughly L-Z. (TEP p.38)

They were split because they have a different theme. First is joy and thanksgiving, then a lament. Convention would have it the other way around. But in the ship of fools, the first shall be last; so forget the labels.
Here David is thankful that his many enemies have been defeated. The modern reader gets little from the superficially triumphal tone except as an example of faith in adversity, or as an allegory of our struggling with our own demons or the ‘Dark Side’. Throughout, we are reminded:
God will be a refuge for the oppressed, a refuge in times of trouble. (v. 9)
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Amongst the early settings is one for double choir by Heinrich Schütz. The illustration shows a little detail of the parts, rather confusingly labelled C A T B 5 7 6 8. Choose your partners and do-si-doh.
Enticed by the Latin feel and enjoyable, if somewhat predictable harmonies, we at SWUC turn to PFAS 9A. A revised refrain text will be drawn from verses 9 and 10 (no, nothing to do with those big fat hens):
The oppressed will find refuge in God who is just
Those who know of your name will in you put their trust.
However, we shall not use any of the suggested chant tones — we have presented several in recent weeks to good effect but it’s time for a change. So to add to the enjoyment, the verses have been paraphrased in blank verse to fit the refrain tune. Here’s an example:
God remembers us all, hears our cry when cast down.
Show your grace when we suffer from those full of hate.