The whole tone is together with the semitone the two smallest intervals in the western music tradition.
But small is not insignificant! Whole and semitones are the main building blocks of musical scales which in turn are the foundation for most musical compositions.
A whole-tone (often shortened to tone), is the distance from one note to the next, exactly two semitones apart higher or lower.
A tone can also be called a whole step and is an interval called a major second as well!
It’s easiest to see this on a piano keyboard:
From every white key to the next, up or down, there is a tone if it has a black key in between.
From every black key to the next is also a tone if it has one white key in between.
So how about between the two white keys; E-F or B-C, that have no black key between? This interval is called a semitone.
With notes on a staff, every step from one note to the next up or down without using sharps or flats is a tone- except between E-F and B-C, as you saw on the keyboard above, these are semitones, or half steps:
Practice your knowledge of tones and semitones! Here are random intervals. Some are a tone apart, and some are a semitone apart.
Hover over the picture to check your answers.
To change a semitone to a tone you need an accidental. A sharp sign (#) raises the note a semitone, and a flat sign (b) lowers the note a semitone.
How would you change these intervals in each measure to become tones?
The wholetone scale uses only tone intervals. It is called a hexatonic scale, since it uses 6 different pitches. It is easy to find on a keyboard. For example, starting from C you will use:
C-D-E-F#-G#-A# and back again to C.
Read more about it and how many whole-tone scales there really are, here: The wholetone scale.