Fix Flextalk buzz: REG_DWORD speaker settings; measured pitch/speed mapping; fixed-gain normalization

docs/NOTES.md

@@ -33,7 +33,9 @@ From `msttsl/mstts.inf` (`[TTSReg]`):
   `HomographDictionary="1 ft_hgrap.dll"`, `ProperNameDictionary="3 ft_namsa.dll"`,
   `LetterToSoundDictionary="4 ft_l2s.dll"`.
 - Options: `...\FlexTalk\2.0\Options` `Gender=Male`, `SampleRate=11025`.
-- Speakers (per-voice settings; names come from these values):
+- Speakers (per-voice settings; names come from these values). **All numeric
+  values must be REG_DWORD**: with REG_SZ the engine reads garbage and
+  synthesizes a monotone buzz (pitch fixed at max, pitch control dead).
   - `{11260610-C84A-11ce-AEC4-0000C0E9CB87}`: Mode Name / Speaker Name
     "Keith Bell", Pitch 27, Speaking Rate 33, Head Size 46, Expression 59,
     Lowering 40, Prominences 17, Age 30, Volume 100.
@@ -71,6 +73,16 @@ final file `WatsonUNInstall.dll` is incomplete).
 - 32-bit engines require a 32-bit prefix (`WINEARCH=win32`).
 - `sudo` on this machine requires a password; installs are manual.
 
+## Engine units (measured)
+
+- speed: MSTTS range 30-450, Flextalk 50-390; the natural rate is about 150 for every
+  voice (duration at 100/200/300 fits a natural value near 140-150).
+- pitch: engine units, roughly linear in F0 near the natural point (~1.1 Hz per unit).
+  Natural values: about 100 (MSTTS), 106 (Keith Bell), 186 (Kerry Watson); Flextalk max 250.
+  Verified with the corrected DWORD registry: Kerry 0 st = 209 Hz, -6 st = 148 Hz,
+  +6 st = 250 Hz (clamped at max); Keith 0 st = 119 Hz, +6 st = 170 Hz.
+- The wrapper maps semitones as `natural * 2^(st/12)` and clamps to the range.
+
 ## Decompiled corpora (Ghidra)
 
 - `/mnt/ghidra/decomp/msttssyn.dll/` (786 functions, engine)