Intervals: Seconds and Thirds
Measuring the distance between two notes, starting with the smallest and most common intervals.
An interval is the distance between two notes, measured in semitones and named by a number (how many letter names it spans) plus a quality (minor, major, perfect...).
A second spans two adjacent letter names (C to D, E to F). A minor second (m2) is one semitone — the smallest interval in Western music, and quite tense-sounding. A major second (M2) is two semitones — the distance of a normal scale step, and sounds much more open.
A third spans three letter names (C to E, D to F). A minor third (m3) is three semitones — it's the interval that gives minor chords their character. A major third (M3) is four semitones — it's what makes major chords sound bright.
In the exercise below, two notes light up on the keyboard. Listen (Play) and look at the gap, then choose the interval.