[Request] Volume slider for Turbo/Alternate Speed

[ImSpecial]

I have a simple requests for this great emulator, would it be possible to add a volume slider for Turbo/Alternate Speed? Currently there's just a Master (global) volume slider and a Mute checkbox, but I'd like to have sound be quieter from that of the Master volume for when turbo/alternate speed is on, for example have Master sit at around 70%, and when Turbo button is pressed have volume go down to around 30%, here's a screen shot of how Bizhawk handles it.

https://i.imgur.com/BvQ3XYR.png

Anyway that's all I had, keep up the great work!