We have moments where we are using the four-to-almost-five-octave range of the choir.

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It involves a degree of variation and improvisation in both vocal parts but always ends with two performers singing in unison or an octave apart.

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Indignation rouged his cheeks, and his voice rose half an octave.

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Where the band fully reveals its talent, though, is on "Petrula the Destroyer, " with its fast-paced start and the jarring pounding of low octave piano chords.

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Am sang "I Gotta Feeling" with octave-hopping pop singer Jessie J, X-Factor alumni JLS produced a medley of hits, while Barlow performed a duet with a painfully out of tune Cheryl Cole.

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In the years since Moreschi last sang, recordings of arias composed for castrati, most of them written by Handel, have been transposed an octave for baritones or are sung by sopranos or countertenors.

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The tuning of the ncegele is based on a division of the octave into five equal intervals, and the sounds are produced by striking the keys with wooden sticks with a rubber beater fitted to the end.

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When at long last some of them were revived in the 1920s, they were severely cut down and many of the lead parts, written for the star castrati of Handel's day, were transposed an octave down for a tenor or a baritone, leaving them barely recognisable.

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