The Masquerade Is Over

Here's a block chart and analysis of the chord structure to "The Masquerade Is Over," based on the version published in the New Real Book volume 1. The A section is 16 measures, the bridge is 8. It's an A A B A form with the first 12 bars the same every time. The 1st ending is a typical turn-around, with iii replacing I so the chord roots move 3-6-2-5. In the 2nd ending the harmonic motion is doubled with 3-6 in measure 29, 2-5 measure 30, then a short cliche where the I chord drops to bVII7 and returns to I for the first two beats in measure 32. On beats 3 and 4 of bar 32 a fully altered dominant sets up the ii chord that starts the bridge.

Taking a closer look at the first 12, to simplify, one can consider the m7-dom.7 combinations as belonging to the dominant chord. That gives us 3 4-measure chunks: I-III7-II7-I7, IV-VI7-II7-V7 and I-I7-IV-bVII. Bar 11 is a Lydian IV chord and 12 is a bVII Lydian dominant. You could use the melodic minor ascending scale relating to ivmMaj7 (or ivm6) when improvising on measure 12 (and 28 & 52 -- it's a 56 measure song 16-16-8-16). 

The 1st ending is a 4 bar turn-around, iii-VI7-ii-V7. The 1st 2 measures of the 2nd ending are those same 4 chords compressed into 2 bars, followed by a cliche stretching the I over 6 beats (it doesn't have to be I-bVII-I...) and VI7 signals the bridge.

The bridge is simply "ice cream changes" every 2 beats starting with minor ii, V7, iii (substituting for I), VI7, ii, V, then pausing for a measure on the I chord. A surprise modulation up a step is one way to describe the next 3 bars... ice cream changes starting over (on I but using the iii substitute) iii(m7b5), VI7, ii, V7 (9 is in the melody), then I7 (v-I7) and modulating back for a ii-V in the original key (measure 40) for the return to the A section.

The last 4 measures ("Coda") are very much like the 2nd ending with a suspended chord for the V in measure 54 releasing to I in measure 55. Bar 56 can be a turnaround when continuing to solos.
Male vocal works well in the published key of Eb, alto sax sounds good in concert F (Lou Donaldson on Blue Note), and female vocal is often in Bb on this one. So learning this (or any tune) according to the numbers makes changing the key a lot easier when called on to do so by the situation.