One of the most useful ways to utilize harmonics, besides color and pitch changes, is to facilitate fast passages in the third octave of the flute.
By using harmonics of the octave or fifth (actually twelfth, but for simplification purposes we’ll refer to them as fifth) we can avoid some of the awkward cross-fingerings inherent to the third octave.
Below let’s examine some passages of the solo and orchestral repertoire where harmonic fingerings come to our help.
In the first movement of Pini di Roma, "I pini di Villa Borghese", Ottorino Respighi writes an F#A3 tremolo in the first flute part.
This tremolo is awkward to play with regular fingerings, and hard to sound with harmonic fingerings (F#1 & A1) without any modifications.