* convert to web components
https://developer.mozilla.org/en-US/docs/Web/API/Web_components
** don't trawl dom when setting up behavior
since it's a custom element, we should know its exact layout at all
times, so ~querySelector~ shouldn't be necessary.

* well-tempered scale
| semi-tones |      freq | just | interval |
|------------+-----------+------+----------|
|          0 |         1 |  1:1 | I        |
|          1 | 1.0594631 |      | IIb      |
|          2 | 1.1224620 |  9:8 | II       |
|          3 | 1.1892071 |  6:5 | iii      |
|          4 | 1.2599210 |  5:4 | III      |
|          5 | 1.3348399 |  4:3 | IV       |
|          6 | 1.4142136 |      | Vdim     |
|          7 | 1.4983071 |  3:2 | V        |
|          8 | 1.5874011 |  8:5 | vi       |
|          9 | 1.6817928 |  5:3 | VI       |
|         10 | 1.7817974 |  9:5 | vii      |
|         11 | 1.8877486 | 15:8 | VII      |
|         12 |         2 |  2:1 | VIII     |
#+TBLFM: $2=2^($1/12)

| degree |       3:2 |     2:1 |
|--------+-----------+---------|
|      1 |      660. |     880 |
|      2 |      990. |    1760 |
|      3 |     1485. |    3520 |
|      4 |    2227.5 |    7040 |
|      5 |   3341.25 |   14080 |
|      6 |  5011.875 |   28160 |
|      7 | 7517.8125 |   56320 |
|      8 | 11276.719 |  112640 |
|      9 | 16915.078 |  225280 |
|     10 | 25372.617 |  450560 |
|     11 | 38058.926 |  901120 |
|     12 | 57088.389 | 1802240 |
#+TBLFM: $2=440*(3/2)^$1::$3=440*2^$1