The Baroque period saw the creation of tonality, an approach to writing music in which a song or piece is written in a particular key; this kind of arrangement has continued to be used in almost all Western popular music. During the Baroque era, professional musicians were expected to be accomplished improvisers of both solo melodic lines and accompaniment parts. Baroque concerts were typically accompanied by a basso continuo group (comprising chord-playing instrumentalists such as harpsichordists and lute players improvising chords from a figured bass part) while a group of bass instruments—viol, cello, double bass—played the bassline. A characteristic Baroque form was the dance suite. While the pieces in a dance suite were inspired by actual dance music, dance suites were designed purely for listening, not for accompanying dancers.
During the period, composers and performers used more elaborate musical ornamentation (typically improvised by performers), made changes in musical notation (the development of figured bass as a quick way to notate the chord progression of a song or piece), and developed new instrumental playing techniques. Baroque music expanded the size, range, and complexity of instrumental performance, and also established the mixed vocal/instrumental forms of opera, cantata and oratorio and the instrumental forms of the solo concerto and sonata as musical genres. Many musical terms and concepts from this era, such as toccata, fugue and concerto grosso are still in use in the 2010s. Dense, complex polyphonic music, in which multiple independent melody lines were performed simultaneously (a popular example of this is the fugue), was an important part of many Baroque choral and instrumental works.
The term "baroque" comes from the Portuguese word barroco, meaning "misshapen pearl". Negative connotations of the term first occurred in 1734, in a criticism of an opera by Jean-Philippe Rameau, and later (1750) in a description by Charles de Brosses of the ornate and heavily ornamented architecture of the Pamphili Palace in Rome. Although the term continued to be applied to architecture and art criticism through the 19th century, it was not until the 20th century that the term "baroque" was adopted from Heinrich Wölfflin's art-history vocabulary to designate a historical period in music.
The term "Baroque" is generally used by music historians to describe a broad range of styles from a wide geographic region, mostly in Europe, composed over a period of approximately 150 years. Although it was long thought that the word as a critical term was first applied to architecture, in fact it appears earlier in reference to music, in an anonymous, satirical review of the première in October 1733 of Rameau's Hippolyte et Aricie, printed in the Mercure de France in May 1734. The critic implied that the novelty in this opera was "du barocque", complaining that the music lacked coherent melody, was filled with unremitting dissonances, constantly changed key and meter, and speedily ran through every compositional device.
The systematic application by historians of the term "baroque" to music of this period is a relatively recent development. In 1919, Curt Sachs became the first to apply the five characteristics of Heinrich Wölfflin's theory of the Baroque systematically to music. Critics were quick to question the attempt to transpose Wölfflin's categories to music, however, and in the second quarter of the 20th century independent attempts were made by Manfred Bukofzer (in Germany and, after his immigration, in America) and by Suzanne Clercx-Lejeune (in Belgium) to use autonomous, technical analysis rather than comparative abstractions, in order to avoid the adaptation of theories based on the plastic arts and literature to music. All of these efforts resulted in appreciable disagreement about time boundaries of the period, especially concerning when it began. In English the term acquired currency only in the 1940s, in the writings of Bukofzer and Paul Henry Lang.