Progression/Modulation Help

[Kneesks]

Hey everyone, me and a friend are co-arranging a Pixar Medley for a concert at my college and I had a quick question for help with it.

The last 2 songs are the A major section of "So Long" by Randy Newman from Toy Story 3 into La Festin from Ratatouille. The main problem I've been having here, is trying to figure out setting up this modulation and time signature change. We are going from a slow 4/4(around 85) to a 3/4 waltz(135-140) and a key change of A major to Eb major.

Any ideas on how to get here in a way that doesn't sound jarring? Writing is for 5 parts.

[Crazy4Tbone86]

Use the G# (leading tone) fully diminished 7th chord, especially if you have a G#, B or D in the melody that you can stop on. That chord is exactly the same fully diminished (leading tone D) for E-flat major. You can even have the B natural drop to a B-flat and the chord becomes a B-flat dominant seventh chord which leads nicely into E-flat major.

[Kneesks]

Use the G# (leading tone) fully diminished 7th chord, especially if you have a G#, B or D in the melody that you can stop on. That chord is exactly the same fully diminished (leading tone D) for E-flat major. You can even have the B natural drop to a B-flat and the chord becomes a B-flat dominant seventh chord which leads nicely into E-flat major.

Mhm, I took these and tried labbing those somewhat in a music writing app and I think theres something getting lost.

So it would go(with small pickup)
2 (in A) 5 7 5 1
Bm7(b5)/F - E7 - G#dim7 - Bb7 - Eb
Or
2 (in A) 5 7(In Eb) 5 1
Bm7(b5)/F - E7 - Ddim7 - Bb7 - Eb
The bass would follow
F - E - G# - Bb - Eb
Or
F - E - D - Bb - Eb

Maybe it's the cadence beforehand? The song resolves on AMaj for several measures, and it is just a triad, so theres no common tones to take from A major and Apply to any EbMaj chords.

[Crazy4Tbone86]

It sounds like you are adhering to the original melody very strictly. Not seeing the score, my guess would be that you will need to alter the melody so that it stalls on a G#, B or D and that would give yo the Liberty to do the modulation.