"Old 100th" or "Old Hundredth" (also commonly called "Old Hundred") is a hymn tune in Long Metre from Pseaumes Octante Trois de David (1551) (the second edition of the Genevan Psalter) and is one of the best known melodies in all Christian musical traditions. The tune is usually attributed to the French composer Louis/Loys Bourgeois (c. 1510 – c.1560).
Although the tune was first associated with Psalm 134 in the Genevan Psalter, the melody receives its current name from an association with the 100th Psalm, in a translation by William Kethe entitled All People that on Earth do Dwell. The melody is commonly sung with diverse other lyrics as well.
The Genevan Psalter was compiled over a number of years in the Swiss city of Geneva, a center of Protestant activity during the Reformation, in response to the teaching of John Calvin that communal singing of psalms in the vernacular language is a foundational aspect of church life. This contrasted with the prevailing Catholic practice at the time in which sacred texts were chanted in Latin by the clergy only. Calvinist musicians including Loys Bourgeois supplied many new melodies and adapted others from sources both sacred and secular. The final version of the psalter was completed in 1562. Calvin intended the melodies to be sung in plainsong during church services, but harmonized versions were provided for singing at home.
The original lyrics set to this tune in the Genevan Psalter are translated from Psalm 134: