This is how the parts interleave in the happy, inanely fun, hyper catchy song from Greetings from Unicornia, made by somebody (maybe @Ilsor >>974908#comment_4197079). Something about it was bugging me, so I checked. Dear Princess Celestia, it’s correct, but I had to check and now I can’t get the damn thing out of my head again. So now I share my pain with you.
 

 

 
Listen: https://www.youtube.com/watch?v=ezfEquAPBd0  
Looping: http://www.youtube.com/watch?v=tdyCIuqnfL8
 

 
Wish You Were Here
 
Music: Terry Sampson  
Lyrics: Lorraine Feather
 
a. (Rarity the Unicorn, voiced by Cathy Weseluck)
 
How we wish you were here,  
If you could appear right here, what fun!  
How we wish you were here,  
To play in the all day sun!
 
May we… de-deedle-dee… de dee-deedle-dee,  
Make one thing clear?  
We do… do-doodle-do… wish you-doodle-do  
Were here!
 
b. (Cheerilee, voiced by Tracey Moore)
 
This is where rainbows all are born,  
Try asking any unicorn.
 
La laa la, laa-ly lally loo,  
Every unicorn knows it’s true!
 
c. (Rainbow Dash, voiced by Venus Terzo)
 
Our crystal carriage is nice and wide  
If you were here, we all could ride.
 
So shi-i-i-iny, so wi-i-ide,  
We know you’d love the ri-i-ide.
 
Parts
 
All parts sing their verses normally, but the parts interleave and repeat. Rarity’s is sung at about twice the rate of Cheerilee’s and Rainbow Dash’s.
 
The main animated Wish You Were Here song has the following arrangement, which is so very nearly the numbers 1 to 7 in binary notation. However, a musical interval steals the 6, and I now realize that this is what was bugging me all along.
 
1 2 4  
a     = 1  
  b   = 2  
a b   = 3  
    c = 4  
a   c = 5  
      ← aaargh! Missing 6!  
a b c = 7
 
Rainbow Dash’s part is rather quiet in the final bit, but it’s there. The end credits have a different, simpler arrangement:
 
a      
  b    
    c  
a b c
 

 
Corrections welcome, DM me!