- This article is about music. For other uses, see Transcription (disambiguation)
In music, transcription can mean notating a piece or a sound which was previously unnotated, as, for example, an improvised jazz solo. Further examples include ethnomusicological notation of oral traditions of folk music, such as Béla Bartók's and Ralph Vaughan Williams' collections of the national folk music of Hungary and England respectively. The French composer Olivier Messiaen transcribed birdsong in the wild, and incorporated it into many of his compositions, for example his Catalogue d'oiseaux for solo piano. Transcription of this nature involves scale degree recognition and harmonic analysis, both of which the transcriber will need relative or perfect pitch to perform.
Transcription may also mean rewriting a piece of music, either solo or ensemble, for another instrument or other instruments than which it was originally intended. The Beethoven Symphonies by Franz Liszt are a good example. Transcription in this sense is sometimes called arrangement, although strictly speaking transcriptions are faithful adaptations, whereas arrangements change significant aspects of the original piece.
In popular music and rock, there are two forms of transcription. Individual performers copy a note-for-note guitar solo or other melodic line. As well, music publishers transcribe entire recordings of guitar solos and bass lines and sell the sheet music in bound books. Music publishers also publish PVG (piano/vocal/guitar) transcriptions of popular music, where the melody line is transcribed, and then the accompaniment on the recording is arranged as a piano part. The guitar aspect of the PVG label is achieved through guitar chords written above the melody. Lyrics are also included below the melody.
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Some composers have rendered homage to other composers by creating "identical" versions of the earlier composers' pieces while adding their own creativity through the use of completely new sounds arising from the difference in instrumentation. The most widely known example of this is Ravel's arrangement for orchestra of Mussorgsky's piano piece Pictures at an Exhibition. Webern used his transcription for orchestra of the six-part ricercar from Bach's The Musical Offering to analyze the structure of the Bach piece, by using different instruments to play different subordinate motifs of Bach's themes and melodies.
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In transcription of this form, the new piece can simultaneously imitate the original sounds while recomposing them with all the technical skills of an expert composer in such a way that it seems that the piece was originally written for the new medium. But some transcriptions and arrangements have been done for purely pragmatic or contextual reasons. For example, in Mozart's time, the overtures and songs from his popular operas were transcribed for small wind ensemble simply because such ensembles were common ways of providing popular entertainment in public places. Mozart himself did this in his opera Don Giovanni, transcribing for small wind ensemble several arias from other operas, including one from his own opera The Marriage of Figaro. A more contemporary example is Stravinsky´s transcription for four hands piano of The Rite of Spring, to be used on the ballet's rehearsals. Today musicians who play in cafes or restaurants will sometimes play transcriptions or arrangements of pieces written for a larger group of instruments.
Other examples of this type of transcription include Bach's arrangement of Vivaldi's four-violin concerti for four keyboard instruments and orchestra; Mozart's arrangement of some Bach fugues from The Well-Tempered Clavier for string trio; Beethoven's arrangement of his Große Fuge, originally written for string quartet, for piano duet, and his arrangement of his Violin Concerto as a piano concerto; Franz Liszt's piano arrangements of the works of many composers, including the symphonies of Beethoven; Tchaikovsky's arrangement of four Mozart piano pieces into an orchestral suite called "Mozartiana"; Mahler's re-orchestration of Schumann symphonies; and Schoenberg's arrangement for orchestra of Brahms's piano quintet and Bach's "St. Anne" Prelude and Fugue for organ.
Since the piano became a popular instrument, a large literature has sprung up of transcriptions and arrangements for piano of works for orchestra or chamber music ensemble. These are sometimes called piano "piano reductions", because the multiplicity of orchestral parts—in an orchestral piece there may be as many as two dozen separate instrumental parts being played simultaneously—has to be reduced to what a single pianist (or occasionally two pianists, on one or two pianos, such as the different arrangements for George Gershwin's Rhapsody in Blue) can manage to play.
Piano reductions are frequently made of orchestral accompaniments to choral works, for the purposes of rehearsal or of performance with keyboard alone.
Automatic transcription 
Several attempts have been made at automatic transcription of music, most of which have qualified for someone's Master's or PhD thesis. However, a collection of the tools created by this ongoing research could be of great aid to musicians. In general, musical recordings are sampled at a given recording rate and its frequency data is stored in any digital wave format in the computer. Such format represents sound by digital sampling.
To transcribe music automatically, several problems must be solved:
1. Notes must be recognized - this is typically done by changing from the time domain into the frequency domain. This can be accomplished through the Fourier transform. Computer algorithms for doing this are common. The Fast Fourier transform algorithm computes the frequency content of a signal, and is useful in processing musical excerpts.
The method proposed in Costantini et al. 2009 focuses on note events and their main characteristics: the attack instant, the pitch and the final instant. Onset detection exploits a binary time-frequency representation of the audio signal. Note classification and offset detection are based on constant Q transform (CQT) and support vector machines (SVMs). An audio example can be found here.
Transcription aids 
Prior to the invention of digital transcription aids, musicians would slow down a record or a tape recording to be able to hear the melodic lines and chords. The problem with this approach is it also changed the pitches, so once a piece was transcribed, it would then have to be transposed into the correct key.
Software designed to slow down the tempo of music without changing the pitch of the music can be very helpful for recognizing pitches, melodies, chords, rhythms and lyrics when transcribing music. The software generally goes through a two-step process to accomplish this. First, the audio file is played back at a lower sample rate than that of the original file. This has the same effect as playing a tape or vinyl record at slower speed - the pitch is lowered meaning the music can sound like it is in a different key. The second step is to use Digital Signal Processing (or DSP) to shift the pitch back up to the original pitch level or musical key.
See also 
- Simon Dixon (May 16, 2001). "Automatic Extraction of Tempo and Beat from Expressive Performances". CiteSeer.IST. Retrieved 2009-10-08.
- Giovanni Costantini, Renzo Perfetti, Massimiliano Todisco (September 2009). "Event based transcription system for polyphonic piano music". ELSEVIER, Signal Processing.
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