So what exactly is a musical interval?
It has two common meanings which are very closely related.
1. The strict definition is "
a measurement of the pitch difference between any two notes". (Just as a "time interval" is a measure of the time difference between two events.)
For example, if we compare a low note such as the low open
6th string of a guitar with the much higher sounding open
1st string, we can hear a big difference in pitch. That's a large (or wide) interval.
If we compare the note on the low open
6th string with the note that we hear from holding that string at the
first fret, we can hear both notes sound low, but the note on the first fret sounds just a little higher than the open string note. That's a small (or narrow)
interval. The study of intervals involves understanding and learning how to name the pitch differences between all notes, from the very small to the very large.
2. Less strictly, an interval can mean: "
any two notes played at the same time or one after the other" - (similar to a chord but consisting of only two notes compared to a chord's minimum of three notes.) These two definitions are so closely related that we can usually ignore the difference between them. They are named in exactly the same way, i.e according to the difference of pitch between them. We often play intervals as
two note chords and, just like chords, they all have their own distinct sound and character.
A large part of the vocabulary of many musicians relates directly to intervals. Words such as
major, minor, diminished, augmented, semitone, thirds, sixths, thirteenths and many more are frequently used here on the forum by some of the more advanced members, who use them as part of their everyday musical language. Most often, we hear them in the context of chords, which means a complete understanding of chords is impossible without an understanding of intervals.