What is a Trio Sonata?

As one of the earliest genres of music for small ensembles, the trio sonata holds a place of special importance in the history of chamber music. In fact, some scholars believe that chamber music originated with the trio sonata. Every major Baroque composer wrote one, and the genre has largely defined modern notions of the sonata in the Baroque era (ca. 1600–1750). The trio sonata also laid the groundwork for chamber music genres of the Classical era (ca. 1750–1820), and its influence can be seen in music composed up to the present day.

To tackle the definition of the trio sonata, let’s start with the basics: 1) what is meant by “trio”? and 2) what is meant by “sonata”?

What Is a Trio?

The trio sonata wasn’t typically written for three players and often didn’t contain three movements. The word “trio” refers to the number of parts.

Now, “parts” can mean different things in different contexts. In music for multiple players—either chamber or orchestral—a “part” is the sheet music that is given to an individual player. (The sheet music with all the parts is usually referred to as the “score.”) However, in the Baroque era, one of the parts was often for “basso continuo,” which comprised a lower-range instrument (like a cello or bassoon) and a keyboard or lute.

The job of the continuo was to reinforce the harmonies of a composition: the lower-range instrument played the lowest note of the harmonies, and the keyboard or lute played all the notes of the harmonies according to numerals and symbols in the music called “figured bass” or “thoroughbass.” These two instrumentalists looked at the same part when performing, and, therefore, even though the trio sonata had three parts, it typically had four players.

But a part can also mean a musical line. A helpful way to think about this is to imagine a chord on the piano as a choir: each note is its own voice. The path each voice takes creates a musical line. Thus, if you play C-E-G followed by F-A-C on the piano, it will require one hand and one person, but it would require three voices and three people to sound those notes in a choir, and which note each voice goes to defines the musical line.

This is how Johann Sebastian Bach thought about keyboard and chamber music: when one of his keyboard fugues is “for three voices,” it means there are three musical lines—not three people playing the keyboard. This thinking extends to his trio sonatas for one or two players. In the former category are the Organ Sonatas, in which each hand is one part and the feet on the organ pedals constitute the other. In the latter category are the sonatas for keyboard (two hands/two parts) and flute, violin, or viola da gamba—a primarily Renaissance and Baroque instrument whose appearance resembles a cello, and whose part in the sonatas is often played on a cello.

In this video of Bach’s C-minor Sonata for Violin and Keyboard (BWV 1017) from a 2022 performance at the Chamber Music Society, notice how the Allegro (four minutes in) opens with two parts in the piano—one in each hand. A third part—the violin—then joins in and imitates the right-hand piano part.

Bach: Sonata in C minor for Violin and Keyboard, BWV 1017

Sonatas for a solo instrument and piano were very common in the Classical era and beyond, and Bach’s conception of the trio sonata for two instrumentalists was foundational in the development of the genre.

What is a Sonata?

Few things in the history of classical music have caused more confusion than the word “sonata.” In the mid-18th century—before the development of the Classical-era sonata form—the French writer and philosopher Bernard Le Bovier de Fontenelle famously exclaimed “Sonate, que me veux-tu?” (“Sonata, what do you want from me?”). This quote was referenced by Jean-Jacques Rousseau when he attempted to define the sonata in his 1768 Dictionnaire de musique—a book that does very little to clarify the actual meaning of the word “sonata.”

In the Classical era, the sonata evolved into a more palpable musical form, usually appearing in the first movement of piano sonatas, string quartets, symphonies, and many other genres. But in the Baroque era, “sonata” was generally a catch-all term for instrumental music. Domenico Scarlatti (1685–1757) composed 555 keyboard sonatas, which are all in one movement and meant as instrumental exercises. Meanwhile, the trio sonata required a variable number of players, had a variable number of movements, and served a variety of social functions. Given the wildly divergent interpretations of “sonata” in the Baroque era, and the fact that the notion of a sonata transformed throughout the 18th century, it is no surprise that the word caused Fontenelle so much distress.

By the end of the 17th century, the Italian concept of the trio sonata had acquired a more concrete meaning—at least in terms of its movement structure. The French composer and music theorist Sébastien de Brossard, in his 1703 Dictionare de musique, separated trio sonatas into two categories: sonata da chiesa (or “church sonata”) and sonata da camera (or “chamber sonata”). The church sonata generally had a four-movement structure: a slow first movement; a fast second movement resembling a fugue (a compositional form with multiple voices and certain sets of procedures); a slow, expressive third movement; and a fast fourth movement, in which bits of musical material are passed between the players. The chamber sonata often had four, five, or six movements: a slow prelude to introduce the work, followed by several movements in the style of dance music.

Brossard wrote that the church sonatas “are what they [Italians] properly call Sonatas,” and this perception seems to have influenced many future composers to adopt this movement structure in their trio sonatas. However, in the 18th century, the barrier between these two types of sonatas dissipated as fugues disappeared from church sonatas and slow, expressive movements appeared in chamber sonatas. It was also common for church sonatas to be performed in secular spaces, thereby diminishing the separation of performance venue. Furthermore, the common dance movements of the chamber sonata found their way into Baroque suites, partitas, and overtures.

A Little Bit of History

In the 16th century, composers transcribed Franco-Flemish songs (madrigals and chansons) for instrumental ensembles and thus created the genre of the canzona. But the texture of these works tended towards sameness—no parts really stood out. With his 1607 collection Il primo libro delle sinfonia e gagliarde, the Italian Jewish composer and violinist Salamone Rossi (ca. 1570–1630) invented the trio sonata, in which two prominent melodic parts are supported by a bass part. This innovation was influenced by virtuosi singers in the Italian courts of his day.

However, the composer who made the genre his own was Arcangelo Corelli (1653–1713). His published trio sonatas—24 church sonatas and 24 chamber sonatas—defined the genre and laid the groundwork for generations of future composers. The first works published by the Danish composer Dieterich Buxtehude (1637–1707) and the Italian composers Tomaso Albinoni (1671–1751) and Antonio Vivaldi (1678–1741) were all trio sonatas. The French composer François Couperin (1668–1733) and the German composer George Frideric Handel (1685–1759) also made important contributions to the genre.

Handel: Trio Sonata in A major for Flute, Violin, and Continuo, Op. 5 No. 1

Corelli’s trio sonatas played an important role in Bach’s approach to his own. However, for Bach, the trio sonata could more accurately be described as an instrumental composition for three parts (or musical lines), in three movements (like the Organ Sonatas, mimicking the three-movement concerto) or four (the slow-fast-slow-fast church sonata scheme). The vast majority of Bach’s trio sonatas were written for one or two players and no continuo—an innovation that transformed the meaning of a “trio sonata” into something quite different from what that term had come to denote. But in the last few years of his life, Bach turned to the traditional format of the genre in his Sonata sopr’il Soggetto Reale (“Sonata on the Royal Theme”). This trio sonata appears in his late masterpiece The Musical Offering (1747), which uses a theme, given to him by Frederick the Great (King Frederick II of Prussia), in a multitude of compositional forms. The king was a flutist, and therefore Bach wrote the sonata for flute, violin, and continuo.

There is a poetic beauty in the fact that Bach, in his final years, chose to take up the chamber music genre of his youth and implement it in such a conventional (by his standards) manner—as if, in his old age, he felt that he no longer had anything to prove. Or perhaps he was moved by a touch of sentimentality, or simply the desire to create new chamber repertoire for the musicians of Frederick’s court (which included his son C.P.E. Bach).

Whatever the case, by the late 18th century, instrumental chamber genres of the Classical era such as the piano trio and string quartet were overtaking the trio sonata in terms of importance. Although the form of individual trio sonata movements was not hugely influential on the development of Classical-era sonata form (as some might assume), the trio sonata as a chamber music genre provided a foundation on which the genres of the subsequent era could be built.

Textures highlighting the individuality of the instruments were always an integral component of the trio sonata, but as composers began to dispense with the continuo, that individuality became more pronounced, more dynamic, like a conversation among friends. And that, more than the form, movement structure, or instrumentation, is the very essence of chamber music.

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Article by Jesse Jennings