The Ruler
The same fret can need another letter
A# and Bb sound alike here, but only one spells F major clearly.
Take the guided lessonRepair a scale with the right pitches and wrong writing
This draft uses A# where F major needs its fourth degree. Change the spelling without changing the sounding pitch.
Letters describe the relationship; accidentals tune it
A diatonic seven-note scale uses each of the seven letters once. Choose the letter for each degree, then sharpen or flatten it to make the distances fit.
F# and Gb are not interchangeable spellings in every key. In G major the seventh letter must be F, so F# is appropriate. Other keys legitimately need Gb.
Meet E# without inventing another fret
C# major requires C# D# E# F# G# A# B#. E# sounds like F and B# like C in this tuning. The names preserve the degree letters.
Major: W W H W W W H
Why is E# a valid name in C# major?
Spelling depends on the musical sentence
Choose sharp when ascending and flat when descending, in every situation.
That can be a useful convention for some chromatic passages. A key's diatonic spelling follows its scale letters in either direction.
Takeaways
- Same sounding pitch does not always mean the same written degree.
- E# and B# are ordinary results of a spelling rule, not extra pitches.