Playing a first-inversion Neapolitan sixth chord in this note's major key produces a chord whose bottom note is a C. A scale played using only white keys is in the Mixolydian mode if it begins on this note. To change this note's natural minor scale to its harmonic minor scale, an F-natural is raised to an F- sharp. The second-lowest-pitched string on a viola is tuned to this note, whose minor key is the relative minor of (*) B-flat major and has 
Playing a first-inversion Neapolitan sixth chord in this note's major key produces a chord whose bottom note is a C. A scale played using only white keys is in the Mixolydian mode if it begins on this note. To change this note's natural minor scale to its harmonic minor scale, an F-natural is raised to an F- sharp. The second-lowest-pitched string on a viola is tuned to this note, whose minor key is the relative minor of (*) B-flat major and has two flats. This note's minor key was used to write Wolfgang Amadeus Mozart's Symphonies No. 25 and 40, while its major key, which has one sharp, was used to write Eine kleine Nachtmusik. For 10 points, name this note which lies a whole step between F and A.