I am vocalist who is trying to learn solfeggio. I purchased Jim Fleser's book, "The Chord Wheel", (published by Hal Leonard), and this app. LOVE them both.
I sing in a choir, and have difficulty finding the lower harmony part, as I sing alto. My habit is to sing the melody, or soprano part. My whole reason for learning Solfège is to try to find and hit a lower, harmonizing note. The great thing about this app, for me, is that when I play the sequence of ascending notes in a scale, (each one a chord), I can hit the root note of the key. It is the fact that the scales ascend in chords that makes it easy for me to find my starting note. That is why I use this app, rather than a piano app, when I am singing with a choir.
The book and app are great for trying to add solfeggio prompts to musical scores. For example, if I am in the key of D, I set the dial to the key of D. Then, I can see at a glance, that
I - Do - D
ii - Re - E
iii - Mi - F sharp
IV - Fa - G
V - So - A
vi - La - B
vii - Ti - C sharp
I also learned a lot about major scale diatonic 7ths. Thanks for the app!