Notes: C, D, Eb, E, F#, G, Ab, Bb, and B - Key: C - Category: Decatonic Scales
The C Messiaen mode 3 uses ten notes per octave. Because of this same reason it is a member of the so called Decatonic -scales that have Ten-note (or Ten-tone). On the piano keyboard, it is made up of four black keys: Eb, F#, Ab, and Bb and five white keys: C, D, E, G, and B. This combination makes this scale - as well as the C Prometheus, C Prometheus Liszt, and C Prometheus Neapolitan - as great choices for composing or improvising music.
If we take a look a the key signature of the C Messiaen mode 3 Scale we can find it has three flats and one sharps. Therefore, on sheet music you will find four accidentals on the score. The notes of this scale are: C, D, Eb, E, F#, G, Ab, Bb, and B.