Louis Marchand (2 February 1669 – 17 February 1732) was a French Baroque organist, harpsichordist, and composer. Born into an organist's family, Marchand was a child prodigy and quickly established himself as one of the best known French virtuosi of his time. He worked as organist of numerous churches and, for a few years, at the French court. Marchand had a violent temperament and an arrogant personality, and his life was filled with scandals, publicized and widely discussed both during his lifetime and after his death. Despite his fame, few of his works survive to this day, and those that do almost all date from his early years. Nevertheless, a few pieces of his, such as the organ pieces Grand dialogue in C and Fond d'orgue in E minor, have been lauded as classic works of the French organ school.

Marchand was born in Lyon. Évrard Titon du Tillet, writing in 1732, described Marchand's father as a "mediocre organist". The son, however, was a child prodigy. According to the same source, Louis became organist of the Nevers Cathedral when he was just 14 years old; Titon du Tillet also states that ten years later, at the age of 24, Marchand obtained a similar position at the Auxerre Cathedral, but contemporary sources seem to indicate that the biographer was wrong, and Marchand settled in Paris before he turned 20. He married a Parisian, Marie Angélique Denis, in 1689, and worked as organist in numerous churches until 1707–8, when he became one of the King's organists at the court. Between 1713 and 1717 Marchand went on a long concert tour of Germany; after he returned, he settled in Paris once again and worked as organist at Église des Cordeliers until his death, augmenting his income with teaching.

Marchand was one of the most famous French virtuosi of his day. Virtually all contemporary sources speak very highly of his organ and harpsichord skills, and some may exaggerate, consciously or not, the way Titon du Tillet did when he spoke of the Auxerre Cathedral appointment. For instance, one account mentions that Marchand was not required to compete for the position of the organist to the King (as was customary). Another claims that, when Marchand first arrived at Paris, he was offered literally all posts that were vacant at the time. Marchand's skills as a performer were enough to fuel speculations in the press, but apparently he also possessed a volatile, flamboyant personality, and was a very difficult person with whom to work. For example, in 1691 Marchand attempted to displace Jean-François Dandrieu's uncle, Pierre Dandrieu, from the latter's position at St Barthélemy, by implying Dandrieu left a prostitute pregnant. Around 1717 he contested with François Couperin for the authorship of Les bergeries, a very popular piece from Couperin's Second livre de clavecin, published that year. Marchand was also rumored to be unfaithful to his wife and also beat her. The couple separated in 1701, but for many years after this, Marie Angélique kept suing the composer for financial settlement. When Marchand left for Germany in 1713, it may have been to escape from his wife's legal threats—however, Friedrich Wilhelm Marpurg reported that Marchand left because Louis XIV exiled the composer for "impertinence." Still another account claims that after Marchand's wife had left him, Louis XIV ordered half the composer's salary to be withheld and paid to her. Marchand, in response, broke off in the middle of a mass where he was playing and, when the king questioned him, responded, "Sire, if my wife gets half my salary, she may play half the service."

Perhaps the most famous anecdote about Marchand is the account of the competition he was supposed to have with Johann Sebastian Bach in Dresden in September 1717. According to Marpurg, Jakob Adlung, and other German sources (the story is not found in any French documents), the two composers were to have a contest in harpsichord performance, and Marchand fled before Bach's arrival, apparently out of fear of being defeated. This story, retold with various embellishments by Bach's later biographers such as Johann Nikolaus Forkel, was only subjected to close scrutiny by late 20th century scholars; no conclusive proof exists that Marchand ran away, or even that he knew the competition was to take place.

Marchand was evidently not interested in publishing his music, and so, despite his popularity, comparatively few of his compositions survive. The losses are particularly substantial in his vocal music: only one cantata survives, Alcione, three Cantiques spirituelles, and a few airs, which were published in various French anthologies of the first half of the 18th century. The opera Pyrame et Thisbé, mentioned by Titon du Tillet, is lost. Marchand's harpsichord music was previously known only by two early suites, published in 1702, and La vénitienne, a short work published in a 1707 anthology. These compositions are generally considered worthy examples of the French harpsichord style, but, as early works, lacking depth. A third book of harpsichord pieces, comprising 14 suites (12 in C minor, 2 in C major), most attributed to Marchand, was discovered in France in 2003.

Twelve of Marchand's organ works were published posthumously, but some 40 more survive in manuscript copies. Yet again most of these works seem to date from Marchand's early years (and stylistically look back to the 17th century, rather than the new galante style), but they include some of his most important music: the massive Grand dialogue in C (1696), which is usually placed as highly as offertories by François Couperin and Nicolas de Grigny; the harmonically sophisticated Fond d'orgue in E minor, and the Quatuor—a rarely seen four-part contrapuntal French form. Modern scholar Geoffrey Sharp divided Marchand's organ output into three distinct groups: pieces influenced by vocal genres, pieces influenced by instrumental genres, and vocal-instrumental hybrid works. He singles out Marchand's manualiter trios and non-contrapuntal works as the composer's most successful pieces. A six-voice Plein jeu from the pieces published posthumously is important historically as the first instance of double pedals in French organ literature.

Jean-Philippe Rameau was among Marchand's admirers, and his pupils included Pierre Dumage and Louis-Claude Daquin. Dumage praised his teacher in the preface to his Premier livre d'orgue (1708), one of the most important works from the late years of the French organ school. Marchand's contemporary Pierre-Louis D'Aquin De Château-Lyon even compared the composer to François Couperin, claiming that, while Couperin had more art and application, Marchand had a more natural, spontaneous musicianship.[8] In addition to his music, Marchand also wrote a treatise on composition, Règles de la composition, which theorist Sébastien de Brossard considered an excellent, albeit short, work.

Although today most of Marchand's extant pieces are regarded as unimportant by most scholars, a few have expressed the opposite view. French musicologist and writer Philippe Beaussant described the composer's work thus: "Though his compositions are skilfully written, their mastery is not obviously admirable as such. They need to be studied closely before they are found to be very great music."