frequencies increase exponentially
Here's 5 octaves of scale step 1s, using 1 as the base frequency:
| octave | freq | power of 2 |
|---|---|---|
| 5 | 16 | 2^4 |
| 4 | 8 | 2^3 |
| 3 | 4 | 2^2 |
| 2 | 2 | 2^1 |
| 1 | 1 | 2^0 |
So we can use binary logarithms to linearize the frequencies. Here's two octaves:
| step | log(2) of freq | |
|---|---|---|
| 1 | 1 | |
| 7 | 1.907 | |
| 6 | 1.737 | |
| 5 | 1.585 | |
| 4 | 1.415 | |
| 3 | 1.322 | |
| 2 | 1.17 | |
| 1 | 1 | |
| 7 | 0.907 | |
| 6 | 0.737 | |
| 5 | 0.585 | |
| 4 | 0.415 | |
| 3 | 0.322 | |
| 2 | 0.17 | |
| 1 | 0 |
The spacing of the scale steps is clearer, for instance, when you use the binary logarithm of a frequency, rather than the frequency itself:
| step | log(2) of freq | difference, in log(2), between steps |
|---|---|---|
| 1 | 1 | |
| 0.093 | ||
| 7 | 0.907 | |
| 0.17 | ||
| 6 | 0.737 | |
| 0.152 | ||
| 5 | 0.585 | |
| 0.17 | ||
| 4 | 0.415 | |
| 0.093 | ||
| 3 | 0.322 | |
| 0.152 | ||
| 2 | 0.17 | |
| 0.17 | ||
| 1 | 0 |
- Now we can see that
- the scale steps are fairly evenly spaced
- the gaps between scale steps 1 and 2, and between 4 and 5, and between 6 and 7 are the same
- the gaps between scale steps 2 and 3, and between 5 and 6 are the same
- the gaps between scale steps 3 and 4, and between 7 and 1 (in the next octave) are the same