Octave Interval

octave overview

An octave spans twelve half steps, from one note to the next note with the same name, for example C up to the next C. Counted in letter names, C D E F G A B C, the upper note is the eighth, which is where the name comes from.

Lesson Steps

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Two notes an octave apart share a name and almost merge into one sound; the upper note vibrates exactly twice as fast as the lower one. Octaves double a line to make it fuller, especially in the bass, and an octave leap is one of the clearest gestures a melody can make.

On the keyboard both notes are always the same color, with eleven keys between them, so the octave has two shapes: from a white key, or from a black key.

The shapes of the octave on the piano

Each shape sits a little differently under the hand, so it is worth knowing them all. Under each keyboard, the same notes are on the staff: played together, then up, then down.

On a white key: C to C

Octaves that share this same shape start on C, D, E, F, G, A, and B. Eleven keys lie in between, six white keys and five black keys.

On a black key: D♭ to D♭

Octaves that share this same shape start on D♭, E♭, G♭, A♭, and B♭. Eleven keys lie in between, seven white keys and four black keys.

Reading the octave on the staff

An octave goes from a line to a space, or from a space to a line, with three lines and three spaces in between.

This is what makes intervals so useful for reading. Rather than naming every note from the clef, we read from one note to the next: once we know where we are, the shape on the staff tells us how far to move. Reading this way is relational rather than absolute, and it is much faster.

It works the same in the treble and bass clef, and at any height on the staff, so a reader who knows the look of an octave recognizes it everywhere.

The octave in the hand

Octaves are played 1 and 5 on white keys, and if it’s comfortable to reach, 1 and 4 on black keys. The hand holds one shape, and the arm carries it. For a smaller finger span, we need to relax and let the hand contract after playing octaves to avoid holding tension and getting tired.

The spacing on the staff and the spacing in the hand belong together. Beyond a fifth the fingers no longer map one to one onto the notes, so it helps to know the span as a whole hand shape: we see the distance on the staff, and the hand opens to it.

Inverting the octave

Moving the lower note of an octave up an octave puts both notes on the same pitch: the octave inverts to a unison. The numbers still add up to nine (8 + 1).

Practice the octave

Play the first shape, C to C, together and then one note after the other, and listen to the sound before moving on.
Find the same shape at every place it occurs on the keyboard (the lists under each image), then the other shapes. Notice how the hand changes as the keys change color, while the sound stays an octave.
Play an octave up from all twelve keys, naming the upper note as we go.
Read it: look for octaves in a piece we know, and before playing each one, name the interval from its look on the staff.
Once the shapes are reliable, play the interval without looking at the hands, feeling the span between the fingers.

Avoid common mistakes with the octave

Collapsing the hand between octaves. When we play a series of octaves, the hand tends to close between them and reopen for the next. Keeping the shape and moving the arm makes octaves more reliable.
Counting keys instead of half steps. The starting key isn’t counted: from C, the first half step is C♯.
Reading every note from the clef. Naming each note separately is slow. Reading the interval from the previous note is what lets the eye stay ahead of the hands.