Harmonization is the process of adding chord accompaniment to a melody. Playing one or more notes with the melody (that is, playing two or more notes at once). One of the best ways people learn to harmonize by ear is by listening to their favorite songs. Whether it's instrumental or vocal, most music has an existing melody.
In your tracks, see if you can identify the melody and harmonies that exist around them. Charlotte plays in the “Swiss Jazz Orchestra” and the “Zurich Jazz Orchestra”, the two great professional bands in Switzerland. This exercise prepares beginning piano students to play jazz standards by mastering 2-5-1 progressions using chord shells on all 12 keys.