isomorphic steps

static/piano/index.html

@@ -31,7 +31,7 @@
     );
   }
 
-  // arrange notes so that moving three keys sideways is exactly an octave. makes it easy to play octaves. everything else is wonky though...
+  // arrange notes "isomorphically". moving sideways is 5 semitones, moving diagonally upwards is 2 semitones.
   function useEqualSteps() {
     const rows = [
       "1234567890-=",
@@ -42,7 +42,7 @@
     tone = {};
     rows.map((row, y) => {
       row.split('').map((key, x) => {
-        const semitone = x * 4 + y - 20;
+        const semitone = Math.floor(x * 5 + y * 2 - 28);
         tone[key] = 440 * 2 ** (semitone / 12);
       })
     });