Compound intervals
Name intervals wider than an octave, such as the ninth and the tenth, by reducing them to simple ones.
Beyond the octave
Intervals within an octave are called simple, and those wider than an octave compound. The counting goes on: after the octave (8) come the ninth (9), tenth (10), eleventh (11), twelfth (12)… Two octaves make a fifteenth (15).
A compound interval has the quality of the simple interval plus an octave: major second + an octave = major ninth.
major ninth, major tenth, perfect eleventh and perfect twelfth above C4
Practice: The ninth
Practice: The tenth
Reduce it to a simple one
To name a compound interval, subtract 7 from its number: a ninth (9) is a second plus an octave, a tenth (10) a third, a twelfth (12) a fifth.
Why 7 and not 8? The bottom note of the octave also counts as the first degree of the new interval: from C to the C an octave higher is eight degrees but only seven steps.
major third and major tenth above C4: the same colour, more spacious
A compound interval sounds more transparent than the simple one, but its colour is the same. A major third and a major tenth are both bright.