Can somebody help me find compatible pieces?

You see, I'm composing this mashup of composers and I got several comments but it basically boils down to these two:

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Your mashup is too Beethoven and Mozart biased

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Your mashup isn't so much a mashup as it is a string of themes. Try putting more pieces together.

I would prefer for the compatible pieces to be not only harmonically compatible but also compatible in these other ways: 

• Tempo(obviously there will be some variability, but the closer to the established tempo for that section, the better) 
• Dynamics(like I don't want a piano dynamic getting overwhelmed by a forte dynamic) 
• Length(for obvious reasons) 
• Time Signature(2/4 against 3/4 just isn't going to sound right, but I would be willing to accept 2/4 against 4/4 and 2/2 against 4/4) 

Here are the pieces I already have in there save the 2 ending sonatas and the bars they correspond to: 

• Rondo a Capriccio - Bars 1-8 
• Symphony no. 40 First Movement, transposed to key signature - Bars 9-17
• Beethoven's Fifth - Bars 18-22 
• Symphony no. 40 First Movement, transposed to key signature - Bars 22-33
• Bach Violin Sonata in G Adagio - Bars 34-41 
• Beethoven's Fifth, now transposed upwards - Bars 42-45 
• Jupiter Symphony Finale - Bars 46-65 
• Pathetique Sonata Second Movement - 66-81 
• Symphony no. 40 Finale, not transposed - Bars 82-99 
• Beethoven's Fifth, now with extended motive - Bars 100-108 

I am only using 3 composers for this, those being Beethoven represented by the piano, Bach represented by the violin, and Mozart being represented by the flute.  

So, will anybody be willing to help me find some compatible pieces? I don't know if it will be possible to find something compatible with Beethoven's fifth or if it is even worth trying. 

Compatible huh? I don't know, but I've seen they sell adapters on Amazon.com, so with some luck you can get something that'll work. You do have to keep in mind that if the composer is 110v you need a step down converter if the other composer is from a 220v country. Mumble mumble, polarity? Wait, what if the composer is AC but the connecting composer is DC? That'll create all sorts of problems.

No, better to just buy your composers in your region, that way you'll be sure they are compatible with whatever it is you want to connect them to.