it sounds as it was made using fm synthesis but try using 2 or more sine/triangle oscillators, set them at different octaves then maybe filter it slightly so some of the higher freqeuncies are rolled off and pitch down the notes as if you were rubbing you hands across a keyboard. id also try setting one of the oscillators off by 5 or 7 semitones
The first video have a sample-reducer/sample&hold effect (often known as bitcrusher) of which the dry-wet mix is controlled by an envelope with a short decay and low sustain so it sounds like a bell.
The other example sounds like a typical 80's keyboard sound.