Key Signatures: Friends or Foes?

Stella Saleh
May 12, 2024
2 min read

Yesterday during a band rehearsal we were practicing scales in the standard Circle of Fifths order. The more scales we played, the more sharps the key signature acquired. Finally we arrived at C#, the scale with seven sharps. As a brass player I internally rolled my eyes, knowing this scale would sound the most out of tune. Before we started playing, the guy next to me turned to me and asked me “Why do we need to use the key signatures? Why can’t they just write accidentals on every note?” In this post I will explain why:

What is a key signature:

“Key signatures in music are a group of either sharp (raised) or flat (lowered) notes that can be found between the clef and time signature on a piece of written music” ToneGym
They show what key the piece/passage is in
Sharps, flats, or naturals used outside of the key signature indicate alterations to the scale.

History

The first known record of written music is from Ancient Greece, but it took over a thousand years for musicians to organize music in the form it is today. Monks living in Europe

A primitive form of key signatures were first introduced in the music of European monks, around 600 CE. The monks would sing traditional religious songs called “plainchant.” Music during this time was written without a staff and notes did not indicate fixed pitches, but the distance between pitches. Around 1000 CE, Guido d’Arezzo, a Benedictine monk, invented the world's first staff. By 1100 the first key signatures would be published, but with only one flat. At this time, the Western Diatonic scale, or the 12 note scale western music uses today, was still in creation.

Why?

Practical:

While today’s composers write using software like Musescore and Sibelius, these resources were not available even 20 years ago. Writing music, like writing literature then, took much longer, and without a “delete” key, one error could mean having to start all over again. If composers wrote accidentals on every single note, the music would look much denser. Additionally, writing individual accidentals would have taken far longer for composers who were paid by the piece, not by hour.

Theory:

Writing a key signature demonstrates the key center (tonic, home key, I) of a piece in a clearly stated way. From this key center, all other accidentals represent alterations to the home scale. When the key signature changes, so does the key center.

C# major scale (no key signature)

Theory: