For 10 points, name this number of instruments in a sextet.
Beethoven's thirteenth string quartet has this number of movements, and the piece "Chi mi frena in tal momento" from Lucia di Lammermoor has this number of singers. A symphony of this number by Mahler contains three hammer blows of fate. F-sharp major has this number of sharps, and a whole tone scale has this number of notes. Tchaikovsky's Pathetique Symphony and Beethoven's Pastoral Symphony also share this number. Darius Milhaud was in a group of French composers named for this number. For 10 points, name this number of instruments in a sextet.
Beethoven's thirteenth string quartet has this number of movements, and the piece "Chi mi frena in tal momento" from Lucia di Lammermoor has this number of singers.
six