Mozart sonata K545, first movement, measure 32, the same key appearing twice, as Db and C#, respectively (see circles in image). Is it because this way it looks more uniform like in the previous measure? Is it also why the accidentals in the bass scales in these two measures are noted the way they appear? Is such consideration a rule to follow or just a preference by the composer?
That D♭ is...odd. Typically the accidentals will be spelled following a few different conventions:
- Following the key of the current section (e.g., if you're in B♭, the notation will in most cases prefer B♭ to A♯).
- Following the direction of resolution (e.g., if something moves up by half step to D, it's easier to spell it as C♯–D than as D♭–D♮).
Following an A-major scale in the left hand and an implied D-minor scale in the right, this note should certainly be spelled as C♯.
The Neue Mozart Ausgabe, by the way, uses a C♯ at this location; you can access the score (but it's not public domain in the US) here. I've only found this erroneous D♭ in the public transcription available here.