Musical Intervals
An interval describes the pitch difference between two notes, measured by counting the letter names or the spaces on a musical staff between the two notes.
Sharp and Flat Keys
The black keys on a piano are called sharps and flats. Sharps raise a note, while flats lower it. They sit between the pitches of the white keys. A sharp is above a specific key, and a flat is below it. For example, the black key above middle C is called C-sharp, and it's also D-flat because it lowers the next white key (D). Notes that describe the same pitch, like C-sharp and D-flat, are called enharmonic.
Symbols placed before a note on a musical staff show sharps and flats.
- A sharp (♯) raises a note's pitch by a semitone.
- A flat (♭) lowers a note's pitch by a semitone.
- A natural (♮) cancels a previous sharp or flat, returning the note to its natural pitch.
You can apply sharps and flats to any note, including those without black keys on the keyboard. For instance, adding a flat to the C note lowers it to the next key on the keyboard, which is B natural (meaning B natural is the same pitch as C flat).
Half Steps and Whole Steps
The smallest interval in Western music is the half step. On a piano, half steps occur between the white keys B and C and between E and F. In other instances, they happen between a white key and a black key (for example, D to D-sharp or F-sharp to G).
Two half steps equal one whole step. The interval between F and G is a whole step. The interval between B and C-sharp is also a whole step.
When you sharpen a note you move the pitch up a half step and when you flatten a note you move the pitch down a half step.
Scale Degrees
The step method helps describe intervals between two notes, but it can get tricky over longer distances. It's simpler to describe intervals using the seven main notes of a scale and relative numbering. You can use the scale numbers to show the basic spacing between notes, which works for any scale.
The degrees of a scale refer to the individual steps or notes within that scale, counted sequentially from the tonic (the first note of the scale) to the octave (the note with the same name as the tonic, but at a higher pitch). Here are the technical names for the different degrees of musical scale:
- Tonic (First (Root))
- Supertonic (Second)
- Mediant (Third)
- Subdominant (Fourth)
- Dominant (Fifth)
- Submediant (Sixth)
- Leading Tone (Seventh)
- Tonic (Eighth (Octave))
When two notes play the exact same pitch, it's called a unison. If two identical notes, eight steps apart, are played, it's called an octave. (The word "octave" comes from the Latin "octo," meaning "eight," because it spans eight notes above the starting note.)
For example, going from middle C to the next C up the keyboard is an octave; F to F is another octave, and so on.
These musical steps are useful for describing intervals between notes. Instead of counting half steps and whole steps, you can describe an interval using these relative numbers. For instance, if you count C as number one (the first degree), D becomes number two, making the interval between them a second. The interval between C and E (the first and third degrees) is a third, and between C and F (the first and fourth degrees) is a fourth, and so on.
Major and Minor Intervals
When you talk about intervals by degree, you also consider the pitches that go beyond the basic notes—like the sharps and flats or the black keys on a keyboard. When counting by degrees, you'll notice that the second, third, sixth, and seventh notes can be conveniently flattened. Flattening any of these notes creates a minor interval. In a major scale, these intervals naturally occur as major intervals.
Perfect Intervals
Some intervals, like fourths, fifths, and octaves, don't have distinct major or minor versions. These intervals are called perfect intervals and exist in one form only. You can't lower a perfect interval to make it minor or raise it to make it major; there's no concept of a minor fifth or a major octave. Due to their acoustical properties, these intervals are considered perfect as they are.
Augmented and Diminished Intervals
When you raise a perfect interval a half step, it's called an augmented interval. When you lower a perfect interval a half step, it's called a diminished interval.
For instance, with C as the starting note, F is a perfect fourth away. Sharpening the F gives an augmented fourth (F-sharp). Similarly, G is a perfect fifth above C. Flattening G results in a diminished fifth (G-flat).
Other intervals, apart from perfect ones, can also be termed diminished and augmented, and they operate differently. To create a diminished interval, you lower a minor interval by another half step. For instance, F to D-flat forms a minor sixth; flattening the D-flat yields a diminished sixth. Similarly, you can form an augmented interval by raising a major interval by another half step. For instance, F to A is a major third; sharpening the A to A sharp results in an augmented third.
Compound intervals
You can keep counting intervals beyond the octave. These intervals are known as compound intervals as they combine an octave with a smaller interval to create a larger one. For instance, a ninth is simply an octave plus a second, an eleventh is an octave plus a fourth, and so on.
Reference
- The Complete Idiot's Guide To Music Theory by Michael Miller