What's the name of this song from Episode 16 of Shingeki no Kyojin?
The song is called 'Call Your Name', arranged and composed by Hiroyuki Sawano.
Here's a link to the part that you mentioned, when they receive their capes: https://www.youtube.com/watch?v=ApU72YmOcY8
This is an AMV of the song (which I have downloaded myself): https://www.youtube.com/watch?v=AZ9kKyo40PY


I would recommend downloading an app called Shazam to help with identifying music and song lyrics 

Hope this helps!