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Hi

How can we identify an interval compound, I mean, how do you know that the interval is 11a (eleventh)? There is a formula?

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How can I say with 100% of sure that the interval above is 11a (e.g)?

I don't think I understand you correctly but an 11th contains 17 half steps and equals an octave + perfect 4th

It also has a name besides being called an 11th but I don't know how it is in English.

So to recognize them learn what intervals they consist of. First find the note up to the octave and then see what's left and figure out what the two intervals make.

The easiest way on sight is the line/space relationship. For example, both a third and a fifth up from a note will all be the same type (all spaces or all lines). An octave is a space note and a line note about the height of the staff.

I agree with Teodor that it's probably easier to break intervals larger than an octave into 2 parts, mainly because the distance gets hard to judge, especially if they are the only 2 notes. But theoretically, if you knew the distance of an 11th on sight, you would confirm that by both notes being the same, either both lines or both spaces. A 10th is probably more common and would be about the same distance, but one line note and one space note.

By the way, we're solely talking about letter names here and not taking into consideration what key we are in, what flats and sharps there are and whether the intervals are major/minor/perfect, etc.

Both of the previous posters are right, and here is a third way: count letters. So from F at the bottom of the staff to B above the staff is 11 letters (F G A B C D E F G A B). Remember to count both your starting note and ending note.

I would agree that learning the line and space patterns is the quickest way to identify intervals. Odd intervals (3rd, 5th, 7th, 9th, etc) are always line-line or space-space, while even intervals (2nd, 4th, 6th, etc) are always line-space.

Once you get into qualities of intervals (major, minor, perfect,etc) counting half steps can help alot.

Why would you need to read intervals beyond an octave?

You see chords in letter name notation such as C13, and if the OP is working with that kind of thing it might be the reason for the question. Some theory books also deal with these intervals. For example, the2nd level of RCM theory rudiments has you identifying "compound intervals" so that C4 to D5 (they provide notation) would be identified in turn as "major 9" or "compound major 2". Maybe the OP is studying that kind of material. (?)

Thank you all

The reason I asked is it would help answer the question better if we knew what purpose they had for it. If it is theoretical, then you can take your time in identifying such intervals and there is a way you can do this that is easy to learn but takes a bit of time. If it is for playing, then there is probably little need to actually identify the interval.

An 11th is also the same as a fourth with the bass note being an octave higher for a fourth, an octave lower in the 11th.
So, if you have a C and F, it,s a fourth if close together in the same octave. It's an 11 if the C is dropped down to the lower octave.
At least that's how I do it, anyway. ;-)

Searom,

Welcome to the Forums! Dr. Detail here. You have received comment from a few very knowledgeable individuals, but not one has picked up on your 11a, whose “a” suffix, I assume, stands for “augmented”.

You are looking for a fool-proof way to determine that a B (natural), more than an octave above an F, forms an augmented 11th. Here is how:
[1] With any interval, consider the lower of the two notes as DO in a major scale, or as the root of a major triad.
[2] Starting with DO or the root as “one”, count scale steps (letter names) up to the upper note.
[3] When arriving at the upper note’s “number” (in your example, number 11), determine if that upper tone is in the major key of your DO or root.
[4a] If your upper note is in the major scale, and it is a 4th, a 5th, an octave, an 11th, or a 12th, then it is a perfect interval. If it is one half-step higher than the diatonic scale tone, then it is augmented. If it is one half-step lower than the diatonic scale tone, then it is diminished.
[4b] If your upper note is in the major scale, and it is NOT a 4th, a 5th, an octave, nor an 11th, nor a 12th, then it is a major interval. If it is one half-step higher than the diatonic scale tone, then it is augmented. If it is one half-step lower than the diatonic scale tone, then it is minor. If it is two half-steps lower than the diatonic scale tone, then it is diminished.

So, in your correct example:
[1] Consider the F as DO, or as the Root.
[2] Starting with the F as “1”, count scale steps up to the B. We arrive at “11”.
[3] B natural is not in the key of F major.
[4a] The upper note is an 11th, and is one half-step higher than the diatonic Bb found in F major. Therefore, F >> B is an augmented 11th.

I wish it were easier - alas, it isn’t.
Ed

Ed, by Do, do you mean the Tonic?

Precisely! Always consider the lower note the Tonic, and always of a MAJOR scale or chord.

Your method is too drawn-out. Simply break the compound interval into an octave and whatever is left, and then add them together. Say you had the G# below Middle C to the E above C5 (an octave above middle C). Break off the lower octave and you have G#4-E5 (or break off the upper octave and you have G#3-E4), a minor sixth in either case. Add 7 to this interval (for the octave) and you get the answer-a minor thirteenth. Multiple posters have already suggested this much simpler and easier method, which doesn't have you wasting time with counting out the entire interval.

I agree that you can use your answer of G#3-E4 to let you get G#3-E5 by knowing you can add an octave to name the interval (You could also call it a 'compound minor 6'). But Ed was also addressing the question of how to get the quality of an interval. The original question involved an augmented interval.

For naming intervals along with their qualities, I learned something similar to what Ed proposes, but within the range of an octave. After that, we simply added the 7 or called it "compound". You are assuming that being able to tell if an interval is major, minor, perfect, dim. or aug. is already known.

For naming the quality of an interval, we take an hypothetical major scale that begins on the bottom note, and count up from the bottom, so that CD = 2, CE = 3, CF = 4 etc. That gives us our 2nd, 3rd, 4th etc. 1, 4, 5, 8 are Perfects. Anything else, if it is a note of that scale, will be major. A semitone (half step) below major is minor; 2 semitones below major is diminished, a semitone below perfect is diminished, and a semitone above major or perfect is augmented for quality. Once you figure that out, you can also deal with intervals above an octave as you say.

There are also tricks, like knowing that an inverted interval will be the opposite and add up to 9. CD = major 2, so DC = minor 9. Perfects stay perfect: CG = P5, GC = P4.

That's what I learned. Do you have other ways of getting at interval qualities, especially ones that might be handier?

Thanks for the clarifications keystring. I think your method of determining the quality might be the best for beginners. Exercises where you have to identify an interval on the staff (with its arithmetic distance and quality) or write a certain interval above a given note will help speed up the learning process. Eventually, you will be able to identify an interval immediately based on experience and recognizing patterns (some related to the positions of the white-key half steps E-F and B-C). (If anyone needs any of this explained, don't hesitate to ask. I'm not sure how clearly I'm actually describing these concepts, which are hard to explain in words.)

The whole point was not to provide a review for those of us who already know; but to offer an absolutely fool-proof method for those of us who do not know. Without a step-by-step (drawn-out?) process, we end up with chord-builders who believe that a B13(#11) contains the note F.

Ed

Or that the leading tone of G sharp minor is G natural, thus the typical D#-G-A# "triad" you get from them as the dominant chord. You'd be surprised how many people try to do fairly complex theory without knowing what a double sharp is.