Unmeasured preludes (the origin of the preludes)

Example of an unmeasured prelude for Lute, Nicolas Bouvier in 1638

The Prelude:

The prelude is a style that is somewhat personal, flexible, and improvisatory. The rationale behind such a conception traces back to the Renaissance and Baroque periods, when very early (notated) preludes appeared and were being developed.

According to the Harvard Dictionary of Music, the noticeable qualities of the prelude are idiomatic virtuosity, rhythmic freedom, and loose thematic construction. The tiento, toccata, ricercar, fantasia, arpeggiata, tastata, and entrada are all virtually identical in style and function to the prelude.

The very early examples of the preludes are thought to be freely composed small improvisatory pieces for organ, lute, and other Renaissance string instruments, and used as an introduction to the main works or a warming up.

Unmeasured preludes:

Example of an unmeasured prelude for Lute, Nicolas Bouvier in 1638
An example of an unmeasured prelude for Lute by Nicolas Bouvier (1638)

In the 17th century, French lutenists and harpsichordists developed the unmeasured prelude. An unmeasured prelude is a prelude with neither time signature nor bar lines and often has very few note-value indications. Because of this, rhythmic interpretation is mostly left to the performer, resulting in the music being highly improvisatory.

Excerpt of unmeasured prelude by Louis Couperin
Excerpt of unmeasured prelude by Louis Couperin

Here is an example of Louis Couperin's unique notation for his unmeasured preludes.

Two samples of unmeasured prelude and fantasy outside France:

An excerpt from Prelude from Sonata No.3 in G minor by a German composer Silvius Leopold Weiss
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Excerpt of Prelude Sonata No3 in G minor by Silvius Leopold Weiss (tablature )
Tablature
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Excerpt of Prelude Sonata No3 in G minor by Silvius Leopold Weiss in Modern Notation
Modern notation
An exerpt of Fantasia in C minor by Silvius Leopold Weiss
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Exerpt of Fantasia in C minor by Silvius Leopold Weiss (tablature)
Tablature
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Excerpt of Fantasia in E minor by Silvius Leopold Weiss (arranged for guitar)
Modern notation, transposed to E minor for guitar