An arranging and orchestration concept that defines the lowest pitches at which intervals (minor second, perfect fourth, etc.), can be clearly perceived without sounding muddy or indistinct. The limits aren’t absolutes, but represent frequencies below which there is a real risk that the resulting sound will not work well within a normal harmonic context.
This theory is built upon some very sound acoustic concepts. Imagine a piano keyboard. We’ll name Middle C (approximately 261.6Hz) “C3.” One octave lower will be C2; another octave down is C1, then to C0, C -1, etc. The lowest note on an 88-key piano (A -1) is vibrating at about 27.5Hz – hardly recognizable as a distinct pitch by itself. If you strike it and the B one whole step above (about 30.9Hz) at the same time, the frequencies of the two notes are less than 3.5 cycles apart. It’s virtually impossible to distinguish the interval.
As intervals increase, the lowest acceptable pitches go down, due to the increased difference in frequencies of the pitches.
Commonly accepted low interval limits are as follows.
- Interval Lowest pitch Second pitch
- Minor second E2 F2
- Major second Eb2 F2
- Minor third C2 Eb2
- Major third B1 D#2
- Perfect fourth A1 D2
- Augmented fourth/
- Diminished fifth B0 F1
- Perfect fifth C#1 G#1
- Minor sixth F1 Db2
- Major sixth F1 D2
- Minor seventh F1 Eb2
- Major seventh F1 E2