The Basilica of Santa Maria Novella is definitely worth a look if you have the time. It's the city's principal Dominican church, and is full of frescos from frescoes from Gothic and early Renaissance masters. You don't need more than 30 - 45 min to take in the whole thing, but don't prioritize it over other sites / churches if you're short on time in Florence.
#19 - proportion Alberti states it is only natural for us to borrow rules of proportion from music-the octave, the fifth, and the fourth. Alberti most certainly borrowed rule of symmetry and proportion in his buildings. santa maria novella - Alberti