Rozina Mahmood

Ground bass

A ground bass is a baseline or chord sequence that is repeated all the way through a piece. It is an ostinato pattern (any musical pattern that is continually repeated) used in the bass. However the only difference between the two is that an ostinato pattern may be very short, but a ground bass can last many bars before it is repeated. Therefore ground bass may be short and simple, or it may be a complete melody. The repeating baseline brings unity to the piece.

The melody and the ground bass do not always start at the same time and the duration of the melody differs. This is shown in the diagram below:

Characteristically, the melodies and harmonies are continually changing above the ground bass to build variety. Ways in which variety is introduced include musical characteristics such as prominent bass, changes of texture, melody and harmony and increasing complexity. Texture describes how the music is layered. Ground bass music is always polyphonic texture, since it uses several layers. Harmony is the sounding of two or more notes of different pitch, at the same time. There are two types of harmonies. A concord is a “nice” sounding chord, since the notes fit together and sound well when played. A discord is a “horrible” sounding chord, since the notes don’t fit together and don’t sound well when played. Discords are there to create attention and are usually followed by concords to make the melody sound right.         Complexity is about making the music become more complicated.

A melody can be changed over the ground bass in the following ways:

  • The melody can be decorated with extra notes and ornaments (such as trills)
  • The rhythm of the melody can be changed, and/or the metre (number of beats to a bar)
  • The tempo (speed) can be changed
  • The harmonies can be changed (concords to discords or vice versa)
  • The mode can be changed from a major key to a miner key or vice versa
  • The melody can be put into the bass or into an inner part
  • The melody can be presented in imitation, fugato or canon (change of texture)
  • A noticeable change of timbre can be made
  • The melody can be turned upside down (inversion)
  • The melody can be absent whilst the harmony or/and rhythm are kept as a remainder
  • A counter melody (one which fits with the tune) can be added
  • Some of the notes in the tune can be taken away, keeping just the most important ones.
  • The rhythm of the tune can be changed,  just stretched out (augmented) or squashed by using shorter note values (diminution)

The music above the baseline changes and grows to a climax. This device often has great dramatic effect. Instruments commonly associated with performing music composed around a ground bass are keyboard (harpsichord and organ), voice and orchestral instruments.

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There are two names for Ground Bass pieces - chaconne and passacaglia. The distinctions are worth noting and certainly exist in plenty of examples. However, composers have not always used the names correctly, so their meanings have become blurred. A chaconne is a series of unbroken variations invented on a recurring chord progression. Indeed, the 'theme' is the chord progression itself. A passacaglia has a more melodic bass line rather than a prescribed series of harmonies. The theme is 'singable'. Passacaglias tend to be in a slow triple meter.

Below is an example of Pachelbel's ground bass. Pachelbel wrote numerous ...

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