What convinces most pianists that Schumann’s “Furchtenmachen” (Frightening) is an expression of fear or perhaps more specifically anxiety, are the markedly impulsive sections that contrast with lyrical, reflective ones.
And not to be overlooked, are the interjections of syncopated SF’s (accentuated outbursts) that are quite STARTLING and must be well communicated in measures 21-24, as well as in the Schneller (“FASTER”) sequences.
The challenge for the player, therefore, is to keep calm, centered, and focused during the agitated measures and not LOSE CONTROL!
Vladimir Horowitz referred to the fire/ice analogy when approaching testy passages. (particularly those in rapid tempo) so I would readily concur with the Maestro that presence of mind under pressure is central to portraying a potpourri of closely spaced, vacillating emotions.
In my instruction, I suggest an approach to the Schneller section that might relax the treble after beats so they don’t sound forced or too vertical, undermining the horizontal thread of notes in the bass. It’s easy for these to intrude if tension permeates the arms, and if harmonic rhythm is ignored.
Finally while “Frightening” may look frighteningly simple at first glance, it’s far from it, given its abrupt mood shifts.