According to your tutorial improvisation starts with one note.
I would say: the work of breathing and sound quality begins with one long sound. Then after some time melodica starts to sound differently. By the way, try not to play loud in high register – it’s influence on the right ear. Breathing exercises for the clarinet, saxophone and trumpet are very suitable. At the same time syllabulary (dictionary of syllables) for melodica is much more flexible ( about this in tutorial later ).
Lowboy ,I am glad that you begin to understand the concept; to me it took about forty-one years!