Ground bass or basso ostinato (obstinate bass) is a type of variation form in which a bassline, or harmonic pattern (see Chaconne) is repeated as the basis of a piece underneath variations. Aaron Copland describes basso ostinato as, "the easiest to recognize" of the variation forms wherein, "a short phrase—either an accompanimental figure or an actual melody—is repeated over and over again in the bass part, while the upper parts proceed normally [with variation]." However, he cautions that, "it might more properly be termed a musical device than a musical form."
Ostinatos are to classical music what riffs are to popular music. They have a large role in improvised music such as in jazz and Baroque music. A "favorite technique of contemporary jazz writers", ostinatos are often used in modal and Latin jazz, traditional African music including Gnawa music and Boogie-Woogie.
Applicable in homophonic and contrapuntal textures they are distinguished as "repetitive rhythmic-harmonic schemes", the more familiar accompanimental melodies, or as purely rhythmic. The technique's appeal to composers from Debussy to avant-garde composers until at least the 1970s "lies in part in the need for unity created by the virtual abandonment of functional chord progressions to shape phrases and define tonality". Similarly in modal music "relentless, repetitive character help to establish and confirm the modal center". Their popularity may also be justified by their ease as well as range of use, though "ostinato must be employed judiciously, as its overuse can quickly lead to monotony".
In popular music, many bass guitar riffs can be regarded as a modern version of the ground bass. Three examples are Pink Floyd's "Money" and "One of These Days" and Black Sabbath's "Planet Caravan". In retrospect, one can consider many repetitive bass patterns in popular music ground basses.
In jazz, arguably the two most famous and recognizable ground basses were penned by Miles Davis in his "All Blues" (from the album Kind of Blue) and by Wayne Shorter in his "Footprints" (became famous from the album Miles Smiles).
Danny Elfman's theme for Men in Black is an ostinato on bass guitar.
Another example for understanding the procedure is the famous tune from ABBA, "Take a Chance on Me". In its video, we can see each of the four members in a different corner of the screen; during the verses, Benny and Björn sing repeatedly "take a chance, take a chance, take a, take a chan-chance", while Agnetha and Frida sing the lyrics.
American drummer Terry Bozzio has made extensive use of the ostinato as a drumset technique. Many examples can be heard on his instructional videos Melodic Drumming and the Ostinato Vol. I, II, and III, as well as his CDs Solo Drum Music Vol. I and II.
American Progressive metal band Dream Theater showcases harmonized guitar-keyboard Ostinatos in songs such as Learning to Live and In the Name of God, and Bass and Chapman Stick in the songs New Millennium, Burning My Soul, and Home.
Many third-wave ska songs utilize an ostinato as a brass melody.
Electronic music, especially that of the dance variety, has relied on ostinato-like basslines, especially that of tunes from the genre relying on the Roland TB-303 synthesizer (which was originally developed in 1982 by Roland as a "bass-player substitute" for guitarists, but gained more favor in later years as a bassline synthesizer in its own right). Since the 303 also has a pattern sequencer as well and can be controlled to play back at various speeds, it is very easy to create ostinato basslines with it, and genres of electronic dance music such as acid house consist of such, created by the 303 and similar synthesizers.
In Indian Classical Music, during Tabla or Pakhawaj solo performances and Kathak dance accompaniments, a conceptually similar melodic pattern known as the Lehara (sometimes spelt Lehra) or Nagma is played repeatedly throughout the performance. This melodic pattern is set to the number of beats in a rhythmic cycle (Tala or Taal) being performed and may be based on one or a blend of multiple Ragas. It is customary, but not absolutely essential, to align the lehra according to the divisions of the Taal. It is done with a view to emphasize the key junctions of the divisions of the Taal. The quintessential idea is to provide a steady melodious framework for rhythmic improvisations, and is relatively free of numerous rules and constraints honoured by Indian Classical Musicians.
The lehra is usually played on the Harmonium, Sarangi or even the Violin. The lehara may be interspersed with short and occasional improvisations built around the basic melody. It is also permissible to switch between two or more disparate melodies during the course of the performance. It requires years of specialist training Taalim and practise Riyaaz to be able to play Lehara with the required Laya(Tempo) and Swara control. It is considered a hallmark of excellence to play lehara alongside a recognised Tabla or Pakhawaj virtuoso. While there may be scores of individually talented instrumentalists, there are very few who are capable of playing the lehra for a Tabla / Pakhawaj solo performance.
Other instruments like Sitar and Sarod have also been used to play the lehara, but very sparingly. E.g. Pandit Ravi Shankar has played a 12 beat lehara on the Sitar for Ustad Allah Rakha during his solo in 1967 at Monterey Music Festival. Similarly Ustad Ali Akbar Khan has played numerous lehras on the Sarod with Pandit Mahapurush Mishra. There maybe other notable artists who may have also played the lehara on other unconventional instruments like Santoor, Bamboo Flute etc.