I'm confused about what's going on here. Is the descending line from E5 flat to G4 the alto voice? Is the bass the 3rds in the bass clef and the tenor and soprano double at the E flat octave? 
Another thing: why is the first E5 flat played by two voices?  
Hopefully this question makes sense.
Thanks[![enter image description here][1]][1]


  [1]: https://i.sstatic.net/wtvfB.png