The word “Ãœbermorgen” means that Nietzsche does not expect much understanding readers in the near future (this is 1888). But it also contains an allusion to the Ãœbermensch, the Overman/Superman.
Thus Spake Zarathustra is primarily concerned with the Superman. And, as we shall see, the Superman is superhuman in relation to mankind as a whole. So what Nietzsche is essentially saying is: “My readers must be relative Supermen!”
There is also mention of the labyrinth. This, along with Nietzsche’s insistence on seriousness and passion, suggests that his readers must be tragic heroes. Perhaps they must also have something monstrous about them.
“New ears for new music” - that is to say: a new taste.
“Enthusiasm” is in my eyes an inadequate rendition of the German Begeisterung. LEO translates this as “ardour, ecstasy, elation, enthusiasm, exaltation, rapture, rapturousness, verve, zeal”. In any case, it would suffice for us to appreciate that the word includes the word Geist, “spirit”, and literally means “spiritedness”. We should not lose our spirit here, gentlemen!