Prolly a missing prim in vm (surely the case if you do Beeper primitiveBeep and hear nothing), otherwise you have sound disabled.

Can check that using:

SoundService soundEnabled

Btw, you changed 

DummySoundSystem class >> #initialize

SoundService register: self.

Why?

This kinda breaks playing anything but beeps with the DummySoundSystem, as all the play.... methods are instance-side, as well as beeps played with the BaseSoundSystem loaded, as: 

Beeper >> #beep

SoundService default new beep 

does not work anymore when the default is an instance as it used to be, and still is with BaseSoundSystem.

Cheers,

Henry