A Mode 2 Scale
A Mode 2 contains 8 notes: A, A♯, C, C♯, D♯, E, F♯, G. It has 4 sharps: A♯, C♯, D♯, F♯. The step pattern is H–W–H–W–H–W–H–W.
Messiaen Mode 2 is the octatonic (diminished) scale. Its 8 notes divide the octave into 4 equal minor-3rd groups, allowing only 3 transpositions. It is the most practically useful of all Messiaen modes.
Mode 2 alternates half and whole steps (identical to the diminished HW scale). With only 3 possible transpositions, it sits between Mode 1's extreme limitation (2) and conventional scales (12). Its 8 notes contain 4 major triads, 4 minor triads, and 4 dominant 7th chords — an extraordinarily rich harmonic palette. Stravinsky, Bartok, and Scriabin used this scale before Messiaen codified it.
Same fingerings as the half-whole diminished scale. In the Messiaen context, use it as vertical chordal color rather than just a linear improvisation tool — stack thirds from different points in the scale to discover unusual voicings that sound both tonal and alien.