Why do we use a key signature?

This short is an excerpt from my " Iceberg video, which you can enjoy in full here:

Brief edited by Rob Goorney

Why do we use a signature?

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  1. Can you explain why sometimes double sharps or double flats are used instead of a note itself?

    1. If you are writing music in the key of C# minor, it’s useful to be able to write B× (B##) so you don’t have to keep cancelling and reinstating the sharp on the C. You could alternatively write C natural and Db, but the effect would then ripple out to Eb and Fb etc., which is very awkard, because the relative major of Db minor is Fb major, which is definitely worse! Also, for certain chords, double sharps and flats are the only way they could be written (eg. If you want someone to play B, C, Db and Ebb at the same time, or alternatively, A×, B#, C# and D – not that common, but I can’t think of any other ways to write it). The other place you might see it is for diminished chords (eg. C, Eb, Gb, Bbb), to emphasise the structure of the chord, though these can normally be written in other ways (eg. C, Eb, F#, A).

    2. If you’re in the key of Gb major for instance, the sixth would be an Eb, but it’s very common to use a flattened sixth in major as a chromatic note as it has a very emotional feeling, it’d be played over top of the tonic or over chords such as a vii°7, ii°, ivm6, or bVImaj7
      As martineyles mentioned, a diminished seventh chord in some keys would have a double flat, like F°7 would be F Ab Cb Ebb, that’s because the seventh degree is being shrunken–diminished–beyond a minor seventh to a smaller interval; however, it shouldn’t ever be notated as the major sixth would, they were incorrect in saying that.
      I don’t know what you mean about C natural and Db, they’re different?

  2. The modification inside the bar is just for that note, or all notes inside the bar?

    1. Normally all notes with that name at that octave to the end of the bar, plus tied notes that continue into the next bar.

    2. All notes on that line within the bar unless otherwise notated.

      Which can be annoying if you have F#, F[], F#, F[], or similar notes, but if you have a lot of sharps in one bar it’s better than having to notate F#, F#, F#, etc.

    3. @@DeltaEntropy If you keep switching between F natural and F sharp you would probably write E sharps and F sharps (if you’re not using E natural) or F natural and G flat (if you’re not using G natural) to avoid having to cancel and repeat the accidentals.

    1. Fat Cats Going Down Alleyways Eating Birds is what I use for Sharps, and BEAD Greatest Common Factor for flats. The note directly above the most recent sharp is the key for sharps (if there’s only an F#, the note right above F is G, if there’s F# and C#, the note right above C# is D, and so on) and the previous flat is the key for flats (You need to just remember F has Bb, but if you see Bb and Eb, the previous flat was Bb, if you see Bb, Eb, and Ab, the previous flat was Eb, and so on). Hope that answers your question.

    2. If you look at the circle of fifths, seven fifths in a row will always make the major scale.
      Find your tonic note on the circle of fifths, using the note to the left/counterclockwise and five to the right/clockwise will give you a major scale, five notes to the left/counterclockwise and one to the right/clockwise will give you a minor scale. There’s not really a mneumonic for knowing what’s in what key specifically, depending on the key, you’ll need to notate with the sharps, counterclockwise, B# E# A# D# G# C# F#. Flats, counterclockwise, depending on the key are also going to be Bb Eb Ab Db Gb Cb Fb. Just like natural notes going counterclockwise are B E A D G C F. I also remember it with the word “bead” and the mathematical initialism “greatest common factor” like Trendy_endy.

    3. Fa Do Sol Re La Mi Si
      Si Mi La Re Sol Do Fa
      I just memorised it straightforwardly

    4. ​@@TheDeadOfNight37This. This, this, this. If you think about the circle of fifths long enough, you will understand easily how key signatures work and essentially also get the concept of major scale modes for free.

    5. For figuring out the number of sharps, use:

      Father Charles Goes Down And Ends Battle

      This acronym is for the circle of fifths, without the accidentals.

      Major scale: C | G | D | A | E | B | F# | C#
      No. of sharps: 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7
      Relative Minor: A | E | B | F# | C# | G# | D#| A#

      After B, the next fifth is an F# (not F natural), thus the change there.

      For figuring out the number of flats, use:

      Battle Ends And Down Goes Charles’ Father

      The order is now flipped, so instead of the following letter being the fifth, the PREVIOUS letter is the next fifth of that scale.

      Major scale: C | F | Bb | Eb | Ab | Db | Gb | Cb
      No. of flats: 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7
      Relative Minor: A | D | G | C | F | Bb | Eb | Ab

      The scale which uses F natural as its fifth is Bb, not B natural, so it changes there as well.

      I hope that clears up any confusion! If you have any more questions, you should ask someone more experienced than me.

  3. I’m used to music with only accidentals in orchestras. It’s great until the conductor asks to rehearse from the key change, which most sections have. With experience, you realise there is normally a double bar line at the key change. The other problems are playing Elgar, or playing in wind bands, which oftens means there will be a key signature, which is to easy to forget about and plays wrong notes when you’re not used to them.

  4. I think it’s cool that you’ve started uploading short videos. Good content!

  5. Even though I already knew these things, you do a great job with clarity, for anyone who has a basic understanding of these general terms.

    Your clarity and simplicity is what I love about your videos 🤘

  6. Sometimes I feel like key signatures can make it more difficult, but it depends on the piece. If I write a piece with an E major key signature (4 #s) but I want to write in Mixo b6, that means I have to manually write in a C natural and a D natural every time one of those notes occurs.

  7. This is nice, but it doesn’t explain, why music that uses scales other than Ionian and Aeolian use the signature of one of them with accidentals in their score.

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