Unit 5 · Lesson 2 of 12 — IB MYP: Personal and Cultural Expression · Communication
Keys, Key Signatures & Home Tone
A key signature establishes the pitch collection a piece primarily uses, while tonic functions as its home tone. Choosing a key affects the notes and harmonic possibilities available to the composer.
In this lesson
Learning Targets
Each section below is labeled with the target it teaches. The questions and your Noteflight task practice every target.
Target 1Connect a key signature to its major key
Target 2Identify tonic as the home tone
Target 3Choose an appropriate beginner key
IB MYP connection
Command terms: IDENTIFY · APPLY
IdentifyApply
Learner Profile · ATL
Knowledgeable · Thinker — Thinking: connect scale and chord knowledge to the melodies and harmonies you build.
Task
Use what you're learning to complete the Noteflight task below, then check your own work before moving on.
Inquiry: How does choosing a key affect which notes and harmonies are available to you as a composer?
Reflect: What did “Keys, Key Signatures & Home Tone” teach you about your own composing choices?
Key words
Words you will use today
Key
A home tone plus the collection of pitches a piece mainly uses around it. A piece “in G major” treats G as home.
Home tone (tonic)
The pitch a melody treats as its resting place (Unit 1). A key is named after its tonic: the tonic of G major is G.
Sharp (♯) / flat (♭)
A sharp raises a note one half step; a flat lowers it one half step. F♯ is the key just to the right of F; B♭ is the key just to the left of B.
Key signature
The sharps or flats written right after the clef at the start of every line. They apply to every note with that letter name, in every octave, for the whole piece.
Major key
The family of keys most of the music in this course uses. C major, G major, and F major are all major keys; the next lesson shows the exact step pattern they share.
The home tone, revisited
Target 2
Home does not have to be C
Every melody you have written so far was in C: C was the home tone, and the melody used the seven letters C D E F G A B. That combination of a tonic and the collection of pitches around it is a key. Composers can put home on any pitch. Moving a whole melody to a new home keeps its shape and its sense of arrival; only the pitch level changes.
01
Tonic C
The second phrase of “Ode to Joy” in C major. The closed ending steps down from D to C and holds it: C is home.
Beethoven, “Ode to Joy,” phrase 2, in C. Tonic (orange) at the end.02
Tonic G
The same phrase with every note moved up a 5th, so it is now in G major. Nothing about the tune changed: it still steps down to its tonic and holds it. Now the note that sounds like home is G.
The same phrase in G major. Tonic G (orange) at the end.03
Finding the tonic
Use the same clues as in Unit 1. The tonic is where a closed ending lands, usually on a strong beat and a long note. It often appears near the start and on strong beats too. By ear, stop a phrase just before its last note: the pitch your ear expects next is almost always the tonic.
Every G (orange): the downbeat of m. 3 and the held ending.
Sharps, flats, and signatures
Target 1
Why a new key needs a sharp or a flat
Moving a melody to a new home changes which piano keys it lands on, and the whole and half steps from the last lesson have to stay the same or the melody sounds wrong. Starting on C, the white keys happen to give exactly the right steps. Starting on G or F, one white key is off by a half step, so it has to be raised with a sharp or lowered with a flat. Instead of writing that symbol on every note, composers write it once, as a key signature.
01
Sharps and flats
A sharp (♯) raises a note one half step: F♯ is the black key just to the right of F. A flat (♭) lowers a note one half step: B♭ is the black key just to the left of B. The symbol is written before the note, on the same line or space.
F raised to F♯; B lowered to B♭. Each change is one half step.02
G major: one sharp
“Joy to the World” descends through every note from tonic to tonic, and its first move is a half step down. From G, the white key F is a whole step down, so F must become F♯. The sharp on the top line, right after the clef, turns every F into F♯.
“Joy to the World” (Mason) in G major. The F (orange) sounds as F♯.03
F major: one flat
From F, the tune’s fifth note has to be a whole step below C, just as F is a whole step below G in the C major version. The white key B is only a half step below C, so B must become B♭. The flat on the middle line, right after the clef, turns every B into B♭.
“Joy to the World” in F major. The B (orange) sounds as B♭.04
From signature to key
No sharps or flats: C major. One sharp (F♯): G major. One flat (B♭): F major. The signature applies to that letter in every octave: in G major, a high F and a low F are both F♯. Then confirm with your ear and eye: the melody should treat the key’s tonic as home.
Course example in G major: both Fs (orange) sound as F♯ with no symbol on the note.
Choosing a key
Target 3
What makes a good beginner key
Every key sounds equally “correct.” Choosing one is a practical decision: it changes which notes you write, where the melody sits on the staff, and which instruments play it comfortably. For your first pieces with a key signature, C, G, and F major are the strongest choices.
01
Few accidentals to track
C, G, and F major have zero or one sharp or flat, so there is only one altered note to keep in mind. In F major, “Ode to Joy” uses two B♭s, and the signature handles both.
“Ode to Joy,” phrase 2, in F major. Both Bs (orange) sound as B♭.02
A range that fits the staff
In F major, the octave from tonic to tonic, F to F, sits exactly inside the five lines of the treble staff. In G major the top G sits just above the staff, and in C major the low C needs a ledger line. If your melody lives mostly between its tonic and the octave above, F major keeps it easiest to read.
“Joy to the World” in F major: F5 (top line) down to F4 (bottom space).03
Fit the performer
Instruments favor certain keys. Violin and guitar music is often in G or D, because those notes match open strings. Band music is often in F or B♭. Voices choose a key that keeps the melody in a comfortable range. Playback on this site is a simple tone, so the choice here is about range and readability, but it matters when real players read your score.
Petzold, Minuet in G: a keyboard piece in G major, and a favorite for beginning string players.
Worked analysis
Target 1Target 2
Reading the key of the Minuet in G
In Unit 1 you saw the Minuet with a ♯ written on one note. Here is its second phrase as Petzold wrote it, with a key signature. Orange marks every F, which the signature turns into F♯, and the final tonic.
Petzold, Minuet in G, mm. 9–16 (original key). Orange = the two F♯s and the final tonic.
Clue
Where
What it tells you
Key signature
One sharp, on the F line
Every F is F♯: the signature of G major
Altered notes
m. 11 (high F♯), m. 15 (low F♯)
The signature covers both octaves; no symbol is needed on either note
Returns to G
Repeated Gs end mm. 10 and 12; high G takes the downbeat of m. 12
The melody keeps coming back to G at important moments
Ending
m. 15 descends A–G–F♯; m. 16 steps up to G, held
A closed ending on G confirms G as the tonic
Model description: The key signature has one sharp, F♯, which points to G major. The melody confirms it: measures 10 and 12 both end on repeated Gs, high G takes the downbeat of measure 12, and the phrase closes by stepping through F♯ up to G, held for the full final measure. Both F♯s, high and low, come from the signature rather than from symbols on the notes. The signature and the closed ending on G agree, so the passage is in G major with G as its tonic.
Notice what the description does: it names the signature and the key it points to, then uses evidence from the melody (strong beats and the ending) to confirm the tonic. Signature plus home tone is how you identify a key.
Check your understanding
Try it before you compose
Pick an answer for each question. You will see right away whether you are correct and why.
0 of 6 correct
1This excerpt has a key signature of one flat. Which major key does it point to?
Target 1
2Play both excerpts. Which one is written in G major?
Target 1
A
B
3Listen only. This is the Minuet in G. Does this phrase end on its tonic?
Target 2
4In this ending of the Minuet, what is the tonic, and what is the best evidence?
Target 2Target 1
5Listen, then choose which excerpt you heard.
Target 1
A
B
6Your melody lives between its tonic and the octave above. In C major, the low C needs a ledger line. Which beginner key keeps the whole octave inside the five lines of the treble staff?
Target 3
Take it to Noteflight
Compare three keys, then write in one
First look at the three beginner key signatures side by side. Then choose one key, write a short melody in it, and make its tonic sound like home at the end.
Your Noteflight task
Compare C major, G major, and F major key signatures. Create a short score in one key and make its tonic sound like home at the ending.