Trio Sonata for Organ No. 3 in D minor

The Trio Sonata in D minor, BWV 527 (also known as Sonata No. 3 for organ or Trio Sonata No. 3) is part of a collection of six trio sonatas for organ, BWV 525-530. These works represent one of Bach's most outstanding contributions to the organ repertoire, adapting the Italian trio sonata genre (typically for two upper melodic instruments and basso continuo) to a single instrument: the organ, with two manuals and obbligato pedal.

The collection BWV 525-530 was compiled in Leipzig between approximately 1727 and 1730 (some sources indicate as late as 1731). Bach's autograph manuscript dates from this period (including corrections and copies by Wilhelm Friedemann and Anna Magdalena Bach). Some individual movements may come from earlier compositions (transcriptions or reworkings of lost or existing instrumental works), but the sonata BWV 527 as such is considered part of this late compilation in Leipzig.

Bach compiled them mainly for his eldest son, Wilhelm Friedemann Bach, who was around 20 years old at the time, so that he could practice and perfect his organ technique (especially the independent pedal). They are considered among Bach's most difficult and mature works for organ, focusing on technical mastery, counterpoint, and the independence of the instrument's voices rather than on everyday liturgical use. The second movement (Adagio e dolce) is a reworking of a lost instrumental work, later reused in the Concerto for Flute, Violin, and Harpsichord in A minor, BWV 1044.

Sonata BWV 527 consists of three movements, following the classical Italian model of sonata da chiesa (without dance):

1. Andante (in D minor) – Moderate opening movement, with a melancholic and devotional character; it begins with a tentative motif and explores modulations and motivic games in dialogue between the upper parts.
2. Adagio e dolce (in F major) – Slow central movement, expressive and lyrical, in the form of an elegant duet between the two upper voices (like a dialogue or flute duet), with continuous pedal accompaniment; notable for its simplicity and sweetness.
3. Vivace (in D minor) – Fast and virtuosic finale, in the form of a two-part fugue with rondo elements; includes imitated triad figures that leap between the voices, with an active and demanding pedal.

Each movement maintains a strict texture of three independent voices, with invertible counterpoint, concertante elements, and a focus on absolute precision. The work is conceived exclusively for organ, simulating the ensemble of a chamber trio sonata (two violins or flutes + basso continuo) with two manuals (right and left for the two upper melodic voices) and obbligato pedal (for the bass voice), often with the second manual an octave lower to vary the color.

It is considered the simplest sonata in the collection in terms of conversation between parts, but technically and contrapuntally demanding.