I hear no sound

Try one of the following to enable the sounds:

1. go to the settings page in the Melody Music Maker, on the right top, select sounds for the chord and lead voices.

2. set appropriate volumes for the chord and lead voice sounds, this can be done below the voice pickers.

3. Increase the volume on the iPad, as Melody Music Maker follows the overall volume of the device. This can be done at the volume-knobs at the outside of the iPad.

The app stops working when I play with more then three fingers

Every iPad has by default enabled the 'multi tasking features' to swipe between apps.

Disable the 'multi tasking gestures'  in the system setting of you iPad and Melody Music Maker will keep on playing. Even when playing with many fingers simultaniously.