A cool chord progression in Tchaikovsky's violin concerto
Audio here at 0’36 (measure 20)
It seems to feature a Neapolitan sixth chord (which follows its applied dominant) and an applied Fr+6.
Don’t hesitate to share your thoughts or correct any mistakes :)
It's cool that the soprano line implies a sequence of V-I relationships but the harmonization is funky. You could argue that the first chord is really a V7(♭5) in second inversion. And the third chord in your analysis should be V^4/2^/IV, which makes a deceptive resolution to the N^6/4^.