Muze Online: lesson 7
The term ‘interval’ refers to the pitch relationship between two notes; it therefore indicates how much higher, or lower, a note is from our starting note. To describe an interval we need two bits of information: the value of the interval itself (i.e. how many notes it is made up of) and the nature of that interval (perfect, major, minor, augmented or diminished). For example, when we look at the E above middle C on the keyboard we can say ‘E is a major third above middle C’; the two notes are separated by ‘a major third’.
Let us break down these two pieces of information:
1) The number of notes: we can work this out from counting through the alphabetical note names (use your fingers or visualise a keyboard if that helps). For the example above (C to E), we can count through the alphabet: C, D, E: therefore, we know that the interval contains three notes – hence it is called ‘a third’. Similarly, C-G would be described as ‘a fifth’.
2) The second part of the interval description gives more precise detail about the number of semitones involved (remember, semitones are the smallest gaps on the piano, between each white key and its adjacent black key). We will look at the different types in more detail now:
The fourth, fifth and unison (same note)/ octave (same note name but 8 notes apart) are all referred to as ‘perfect’ intervals.
The second, third, sixth and seventh are all referred to as either major or minor intervals: a major interval will follow the key signature of the starting note (e.g. C-E is a major third because E natural is in the key of C major), however, if the third is lowered b a semitone, then it is referred to as ‘a minor third’ (because E-flat is not in the key signature of C major, it is in the key signature of C minor).
Each of the intervals thus far described can be lowered (diminished) or increased (augmented) further. This is uncommon and can result in double sharps (##) or double flats (bb). We will now look at two different examples for perfect and non-perfect intervals:
A perfect fourth: C-F is a perfect fourth. A diminished fourth would be spelt as E – F-flat (which would sound like a major third C-E because E natural is the enharmonic equivalent of F-flat). C-F-sharp would be referred to as ‘an augmented fourth’ because it has increased the interval of a fourth by one semitone. Coincidentally, C-F-sharp would sound identical to C-G- flat (because F-sharp and G-flat are enharmonic equivalents of each other), therefore the interval may be described as either an augmented fourth or a diminished fifth if one was listening to a piece of music, however, only one answer can be correct when reading music since the notes on the stave will determine whether the interval has resulted from an act of diminishment (G becoming G-flat) or augmentation (F becoming F-sharp).
A major third: C-E is a major third. C – E-flat is a minor third. If we lower the E by another semitone, it becomes E-double-flat. If we augment the interval - raising the E by a semitone - then it becomes C – E-sharp, and we have ‘an augmented third’. As you may have realised, these diminished and augmented intervals are unlikely to come up, since it is usually much simpler to write C-D, and C-F rather than C – E-double-flat and C – E-sharp. We use accidentals to demonstrate any raising or lowering of the pitch (any increase or decrease in the interval). To help make sense of these increases and decreases we can use a keyboard or a visual leapfrog method as shown below:
(You can see from the diagram how enharmonic equivalents work – each black note functions as both a sharp for the note below/ to the left of it and a flat for the note above/ to the right of it).
Overall, these are the different intervals possible: unison, second (major or minor), third (major or minor), fourth (perfect), fifth (perfect), sixth (major or minor), seventh (major or minor), octave (perfect).
You can hear these different intervals and their various forms through the audio clips provided.
Once we get to any intervals greater than an octave, they become ‘compound intervals’ e.g. a ninth is made up of an octave and a second, so it is referred to as a ‘compound second’.
Here are some questions to test your knowledge:
1) Please write out the enharmonic equivalents for the following notes:
2) Label each of the following intervals, using the full 2-part description (e.g. C-E is a ‘major third’)
C – E-flat
F-sharp – B
G – C
G – G (this has two possible answers)
D – F
D – F-double-sharp
F – A-double-flat