Logarithmic mapping for volume

src/mididevice.cpp

@@ -426,9 +426,9 @@ void CMIDIDevice::MIDIMessageHandler (const u8 *pMessage, size_t nLength, unsign
 							{
 								LOGNOTE("MIDI-SYSEX: Set Audio Output Level Attenuator %d to %d", nTG, val & 0x0F);
 								// Example: F0 43 10 04 1A 00 F7 to F0 43 10 04 1A 07 F7
-								// Exponential mapping like on the TX816: 7=127, 6=63, 5=31, ... 0=0
+								// Logarithmic mapping for volume
 								unsigned attenVal = val & 0x07;
-								unsigned newVolume = (attenVal == 0) ? 0 : (127 >> (7 - attenVal));
+								unsigned newVolume = (unsigned)(127.0 * pow(attenVal / 7.0, 2.0) + 0.5);
 								m_pSynthesizer->SetVolume(newVolume, nTG);
 							}
 							break;