E♯ (German: Eis)5 is a common enharmonic equivalent of F, but is not regarded as the same note. E♯ is commonly found before F♯ in the same measure in pieces where F♯ is in the key signature, in order to represent a diatonic, rather than a chromatic semitone; writing an F♮ with a following F♯ is regarded as a chromatic alteration of one scale degree. Though E♯ and F♮ sound the same in any 12-tone temperament, other tunings may define them as distinct pitches.
Demorest (2001, p. 46) - Demorest, Steven M. (2001). Building Choral Excellence: Teaching Sight-Singing in the Choral Rehearsal. New York: Oxford University Press. ISBN 978-0-19-512462-0. https://books.google.com/books?id=8zAIcx-t2koC&pg=PA46 ↩
Griffiths (2004, p. 617) - Griffiths, Paul (7 October 2004). The Penguin Companion to Classical Music. Penguin UK. ISBN 9780141909769. https://books.google.com/books?id=04vDuG_pElwC ↩
Zundel (1848, p. 24) - Zundel, John (1848). The Complete Melodeon Instructor, in Seven Parts: Designed as a Thorough Instruction Book for the Melodeon, Seraphine, Eolican, Melopean, Organ, Or Any Similar Instrument. O. Ditson. https://books.google.com/books?id=IrgsAAAAYAAJ ↩
Suits, B. H. (1998). "Physics of Music Notes - Scales: Just vs Equal Temperament". MTU.edu. Michigan Technological University. Archived from the original on 27 November 2023. Retrieved 5 February 2024. https://web.archive.org/web/20231127155251/https://pages.mtu.edu/~suits/scales.html ↩
Griffiths (2004, p. 399) - Griffiths, Paul (7 October 2004). The Penguin Companion to Classical Music. Penguin UK. ISBN 9780141909769. https://books.google.com/books?id=04vDuG_pElwC ↩