During the second half of the 17th century, German composers started pairing preludes or sometimes toccatas with fugues in the same key ; Johann Pachelbel c. Bach's organ preludes are quite diverse, drawing on both southern and northern German influences. Most of Bach's preludes were written in the theme and variation form, using the same theme motif with imitation, inversion, modulation, or retrograde the theme as well as other techniques involved in this baroque form.
Johann Caspar Ferdinand Fischer was one of the first German composers to bring the late 17th-century French style to German harpsichord music, replacing the standard French ouverture with an unmeasured prelude. Fischer's Ariadne musica is a cycle of keyboard music which consists of pairs of preludes and fugues; the preludes are quite varied and do not conform to any particular model.
Ariadne musica served as a precursor to Johann Sebastian Bach's The Well-Tempered Clavier , two books of 24 "prelude and fugue" pairs each. Bach's preludes were also varied, some akin to Baroque dances, others being two- and three-part contrapuntal works not unlike his inventions and sinfonias.
Prelude | Definition of Prelude by Merriam-Webster
Bach also composed preludes to introduce each of his English Suites. The Well-Tempered Clavier influenced many composers in the coming centuries, some of whom wrote preludes in sets of 12 or 24, sometimes with the intention of utilizing all 24 major and minor keys as Bach had done. While other pianist-composers, including Muzio Clementi , Johann Nepomuk Hummel and Ignaz Moscheles , had previously published collections of preludes for the benefit of pianists unskilled at improvisatory preluding, Chopin's set renewed the genre.
Chopin's set served as a model for other collections of 24 or 25 piano preludes in the major and minor keys, [3] including those by Charles-Valentin Alkan Op. Claude Debussy — wrote two books of impressionistic piano preludes which, unusually in this genre, carry descriptive titles.
Preludes were also incorporated by some 20th-century composers into Baroque-inspired suites: As well as a series of unattached piano preludes Op. Some avant-garde composers have also produced unattached preludes. From Wikipedia, the free encyclopedia. For the record label, see Intrada Records. For the ballet, see Praeludium ballet.
Prelude (music)
For a piece for piano by Graham Waterhouse, see Praeludium Waterhouse. This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. November Learn how and when to remove this template message. ReadPrec [ Maybe a] Source. Lift a semigroup into Maybe forming a Monoid according to http: The maybe function takes a default value, a function, and a Maybe value. If the Maybe value is Nothing , the function returns the default value. Otherwise, it applies the function to the value inside the Just and returns the result.
Read an integer from a string using readMaybe. If instead we fail to parse an integer, return 0 by default:. Apply show to a Maybe Int.
If we have Just n , we want to show the underlying Int n. But if we have Nothing , we return the empty string instead of for example "Nothing":. The Either type represents values with two possibilities: The Either type is sometimes used to represent a value which is either correct or an error; by convention, the Left constructor is used to hold an error value and the Right constructor is used to hold a correct value mnemonic: The Left constructor can be used only on String s, and the Right constructor can be used only on Int s:. The fmap from our Functor instance will ignore Left values, but will apply the supplied function to values contained in a Right:.
The Monad instance for Either allows us to chain together multiple actions which may fail, and fail overall if any of the individual steps failed. First we'll write a function that can either parse an Int from a Char , or fail. The following should work, since both '1' and '2' can be parsed as Int s. But the following should fail overall, since the first operation where we attempt to parse 'm' as an Int will fail:. ReadS [ Either a b] Source. ReadPrec Either a b Source.
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ReadPrec [ Either a b] Source. Case analysis for the Either type. If the value is Left a , apply the first function to a ; if it is Right b , apply the second function to b.
We create two values of type Either String Int , one using the Left constructor and another using the Right constructor. Then we apply "either" the length function if we have a String or the "times-two" function if we have an Int:. ReadS [ Ordering ] Source. ReadPrec [ Ordering ] Source.
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A character literal in Haskell has type Char. To convert a Char to or from the corresponding Int value defined by Unicode, use toEnum and fromEnum from the Enum class respectively or equivalently ord and chr.
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ReadS [ Char ] Source. ReadPrec [ Char ] Source. Used for marking occurrences of Char. A String is a list of characters. String constants in Haskell are values of type String. All the basic datatypes exported by the Prelude are instances of Eq , and Eq may be derived for any datatype whose constituents are also instances of Eq.
The Haskell Report defines no laws for Eq. For example, for a type representing non-normalised natural numbers modulo , a "public" function doesn't make the difference between 1 and It is expected to have the following properties:. Note that due to the presence of NaN , Double 's Eq instance does not satisfy reflexivity. Also note that Double 's Eq instance does not satisfy substitutivity:.
Note that due to the presence of NaN , Float 's Eq instance does not satisfy reflexivity. Also note that Float 's Eq instance does not satisfy substitutivity:. The Ord class is used for totally ordered datatypes. Instances of Ord can be derived for any user-defined datatype whose constituent types are in Ord.
The declared order of the constructors in the data declaration determines the ordering in derived Ord instances. The Ordering datatype allows a single comparison to determine the precise ordering of two objects. The Haskell Report defines no laws for Ord. Using compare can be more efficient for complex types. Note that due to the presence of NaN , Double 's Ord instance does not satisfy reflexivity. Also note that, due to the same, Ord 's operator interactions are not respected by Double 's instance:. Note that due to the presence of NaN , Float 's Ord instance does not satisfy reflexivity.
Also note that, due to the same, Ord 's operator interactions are not respected by Float 's instance:.
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Source Contents Index base Instances Bounded Bool Source Since: ReadS [ Bool ] Source readPrec:: Associated Types type Rep Bool:: Bool Source otherwise is defined as the value True. Instances Monad Maybe Source Since: Maybe a Source mplus:: ReadS [ Maybe a] Source readPrec:: Associated Types type Rep Maybe a:: Maybe a Source mappend:: Associated Types type Rep1 Maybe:: Examples Expand Basic usage: If instead we fail to parse an integer, return 0 by default: But if we have Nothing , we return the empty string instead of for example "Nothing": The Left constructor can be used only on String s, and the Right constructor can be used only on Int s: Either String Int The fmap from our Functor instance will ignore Left values, but will apply the supplied function to values contained in a Right: Instances Show2 Either Source Since: Associated Types type Rep1 Either a:: ReadS [ Either a b] Source readPrec:: Associated Types type Rep Either a b:: Examples Expand We create two values of type Either String Int , one using the Left constructor and another using the Right constructor.
Then we apply "either" the length function if we have a String or the "times-two" function if we have an Int: Instances Bounded Ordering Source Since: ReadS [ Ordering ] Source readPrec:: Associated Types type Rep Ordering:: Instances Bounded Char Source Since: ReadS [ Char ] Source readPrec:: It is expected to have the following properties: