Os justi (Bruckner)

 ('The mouth of the righteous'), WAB 30, is a sacred motet composed by Anton Bruckner in 1879. is a Gregorian chant used as gradual of the , and as introit I and gradual II of the .
History.
Bruckner composed this gradual on 18 July 1879 and dedicated it to Ignaz Traumihler, choirmaster of St. Florian Abbey.
When Traumihler saw the manuscript, he asked: "" (Is this the whole text?) Therefore, Bruckner added on 28 July 1879 a verse "Inveni David" in Gregorian mode followed by a repeat of the "Alleluja".
While the first performance was expected on Traumihler's name-day (31 July 1879), it finally occurred four weeks later on 28 August 1879 on the feast of Saint Augustinus. Traumihler conducted while Bruckner played the organ.
The work was first edited by Theodor Rättig, Vienna in 1886, together with three other graduals: "Locus iste", "Christus factus est" and "Virga Jesse". In this first edition, something went wrong: the motet and the first "Alleluja" were issued, but not the extra verse ("Inveni David") and the repeat of the "Alleluja". The extra verse and the repeat of the "Alleluja" were — wrongly — classified by Grasberger as a separate work ("Inveni David", WAB 20).
The full original setting, the manuscripts of which are archived at the "Österreichische Nationalbibliothek", is put in Band XXI/28 of the .
Text and music.
The text of the motet is two verses of Psalm 37, which is Psalm 36 in the Vulgata (). The text of the added verse is taken from Psalm 89 ().
The original work of 18 July 1879, a 69-bar gradual, is scored in Lydian mode for choir "a cappella".
On two occasions (bars 9–13 and 51–56) the choir is divided into eight voices. The second part on "Et lingua ejus" (bars 16–42) is a fugato without any alteration. The last sentence, on "et non supplantabuntur" (bars 65-69), is sung "pianissimo" by the soprano, on a sustained tonic chord by the five other voices (). It is followed by a two-bar unison "Alleluja" in Gregorian mode.
On 28 July 1879, Bruckner added an extra verse "Inveni David" scored for unison male voices with organ accompaniment, and a repeat of the 2-bar "Alleluja". According to Elisabeth Maier the melody of the "Alleluja" is a quote of the "Alleluja" of the introit "In medio ecclesiae" of the "Missa de Doctoribus". The extra verse is apparently Bruckner's own composition.
Traumihler was a fervent supporter of the Cecilian Movement; the reason why Bruckner composed this motet in Lydian mode, without any alteration in the key and in the whole score, and with large use of unaltered chords.
Selected discography.
The first recording of "Os justi" occurred in 1931:
The large majority of the recordings follows the first edition, sometimes without "Alleluja". A selection among the about 120 recordings:
There are only a few recordings with the full motet, i.e., with the verse Inveni David: