To fix this, make sure that the volume is set to high for all levels.
Please go to Window's control panel, and click on the Sound icon. Make sure that the "MIDI" volume is set to high. It is possible that the "Wave" sound is high - which makes you hear some of the sounds, but that the "MIDI" volume is low, making the other silent. Please double check that all "outputs" are set to maximum, and then
control your volume using the "Master Level".
Once all levels are set to high, you should be able to hear all sounds.