Questions: Identifying Intervals by Letter Name Counting

Question 1

What is the generic interval from D up to A?

• A. A fourth
• B. A fifth
• C. A sixth
• D. A seventh

Answer: (B)

Count letter names inclusively: D (1), E (2), F (3), G (4), A (5). Five letter names = a fifth. The inclusive counting rule — including both the starting and ending note — is essential. A student who counts only the steps between notes would get four, arriving at the wrong answer of 'fourth.' Always begin your count at 1 with the lower note, not at 0 or 1 with the first step above it.

Question 2

A student counts the interval from C to G and arrives at 'four.' What error did they make?

• A. They used incorrect letter names — C and G are not adjacent in the musical alphabet
• B. They forgot to count the starting note C, so they counted four steps (C→D→E→F→G) rather than five letter names (C, D, E, F, G)
• C. They should have counted semitones instead of letter names
• D. They needed to account for accidentals before counting

Answer: (B)

The error is non-inclusive counting — treating C as 'zero' rather than 'one.' The correct count is: C (1), D (2), E (3), F (4), G (5) = five letter names = a fifth. This is the single most common mistake in interval identification. Think of it like floors in a building: standing on the first floor and going up to the fifth floor means you count 1, 2, 3, 4, 5 — the floor you start on counts. Accidentals (option D) do not affect the generic interval name, only the quality.

Question 3

C to E♭ is a second because the flat makes E♭ closer to C than E natural is.

• T. True
• F. False

Answer: False

C to E♭ is a third — the same generic interval as C to E natural. Generic interval names are determined entirely by the number of letter names spanned (C, D, E = three), not by the number of semitones or the distance in pitch. The flat on E changes the interval's quality (from major third to minor third) but does not change its generic name. A flat on E does not turn E into a D; it is still E in the letter-name sequence.

Question 4

C♯ to E♯ is a third, just as C to E is a third, because both pairs span the same three letter names.

• T. True
• F. False

Answer: True

Generic intervals depend only on letter names, not accidentals. C♯ (1), D (2), E♯ (3) — three letter names, so a third. C (1), D (2), E (3) — also a third. The accidentals change the quality (C to E is a major third; C♯ to E♯ is also a major third; C to E♭ is a minor third), but the number-name stays the same. This is why the generic interval and the interval quality are learned as two separate but related concepts.

Question 5

A student knows that C to E is a major third and immediately concludes that C♯ to E♭ is not a third at all. Are they correct? Explain.

Model answer: No. C♯ to E♭ is still a third generically — it spans three letter names (C, D, E). However, it is a diminished third in quality: C♯ to E would be a major third (4 semitones), and lowering the top note by a half step makes it C♯ to E♭ = 3 semitones, which is a diminished third. The generic name (third) stays fixed by the letter-name count; accidentals affect only the quality.

The two-part system of interval naming — generic name from letter-name counting, quality from semitone counting — means that accidentals never change the first part. Any pair of notes whose letter names are C and E form some kind of third: major, minor, augmented, or diminished. The student's error is conflating quality with generic name and thinking that an unusual quality (diminished) means the generic name changes too. It doesn't: the letter names are the ground truth for the number.