To make things easier , G-sharp major is usually written as its enharmonic equivalent of A-flat major . However , it does appear as a secondary key area in several works in sharp keys , for example in the Prelude and Fugue in C sharp major from Bach 's Well-Tempered Klavier , Book 1 . For clarity and simplicitly , G-sharp major is usually notated as its enharmonic equivalent of A-flat major ; however , it does appear as a secondary key area in several works in sharp keys - most notably in the Prelude and Fugue in C sharp major from Bach 's Well-Tempered Klavier , Book 1 .