# Does the name of an interval change if the notes are in different octaves?

The interval between C and G is a perfect fifth (P5).

But if the G is in a different octave does the interval name stay the same?

• No. The interval from a C to the G an octave and a half above is a twelfth. If the G is even higher you need to describe it by saying something like "...from the C to the G three and a half octaves higher." Of course if the G is BELOW the C it becomes a perfect fourth if it's close, an eleventh if it's in the octave below, and needs to be described if it's even lower. – Old Brixtonian Sep 27 at 3:13
• @OldBrixtonian ok! Thanks! – Randy Zeitman Sep 27 at 3:26
• I’ve never thought about this, but the question is legitimate: we name the intervals up to 16 but then we add the numbers of octaves. – Albrecht Hügli Sep 27 at 5:18
• @OldBrixtonian Any particular reason why that's a comment? That could have been an answer right there. You pretty much answered all parts of OP's question, and then some. – user45266 Sep 28 at 2:00
• @user45266 Just modesty! And if I convert it to an answer now it'll mess up the threading. But thanks for your kind words. – Old Brixtonian Sep 28 at 7:00

One concept that I might add is the distinction between simple and compound intervals.

Simple intervals are intervals of one octave and smaller; compound intervals exceed the span of an octave.

So this C up to G is a fifth. If we move the C down an octave (or the G up an octave), this becomes a twelfth, but we can also call it a "compound fifth," meaning that it's a fifth, but one larger than an octave.

To quickly translate between simple and compound versions of intervals, just remember the "Rule of 7": subtract or add by 7 to move octaves. Thus an 11th is actually just a compound fourth, because 11-7=4.

• Now we're talking. Never heard of that. Rule of Seven = Modulo 7. "In computing, the modulo operation finds the remainder after division of one number by another (called the modulus of the operation)." en.wikipedia.org/wiki/Modulo_operation – Randy Zeitman Sep 27 at 16:03
• @RandyZeitman Exactly! What we call "diatonic space" is really a mod-7 space, which allows this Rule of 7 to take place. Good catch! – Richard Sep 27 at 16:38
• @Richard Yep! That is exactly how I describe it in my upcoming video about learning music theory. Keys are a helix and each segment is found by 'inclusive counting, by 5's, in base-7'. 1-2-3-4-5(key! G) 5-6-7-(8/1)-2 (key! D) 2-3-4-5-6 (key! A) – Randy Zeitman Sep 27 at 16:48

Any interval is the space between two notes. For naming, two facts are needed. Names of notes, and number of semitones between them.

So, it stands to reason that the interval name for C>E (M3) will not be the same for C>an E an octave higher.That is M10.

In every case, half the interval name stays the same! C> any E will always be M, but the number attached will vary.

If C stays in the same place and G goes an octave higher, then yes, names changes. But if bouth of them moves to one side, then they don't change

• Yes, then they wouldn't be in different octaves. – Randy Zeitman Sep 27 at 16:01

The intervals are counted in the first 2 octaves like this:

1 - Prime

2 - Sekunde

3 - Terz

4 - Quarte

5 - Quinte

6 - Sexte

7 - Septime oder Septe

8 - Oktave

9 - None

10 - Dezime

11 - Undezime

12 - Duodezime

13 - Tredezime oder Terzdezime

14 - Quartdezime

15 - Quintdezime oder Quindezime oder Doppeloktave

Source: German wiki site

https://de.wikipedia.org/wiki/Intervall_(Musik)