Trying to get send_file to work with audio files.

I'm writing a Ruby on Rails application which allows a user to upload
an mp3 file, then play it back. I have it working to the point where a
user can do those things, BUT there is an issue when seeking through
the song. If a user seeks ahead (or lets it play) to a spot in the
song, usually about 2/3 or 3/4 the way through the song, then attempts
to seek back to the beginning (for example 0:20), the play timer will
go to 0:20, like it should but the actual audio will start over again
as if the user seeked to 0:00.

Right now I'm simply attempting to get the song to play in chrome's
basic html5 mp3 player that it uses when passed an mp3 file. This is
the code I'm using to serve up the file, hopefully with all the
correct headers:

http://privatepaste.com/8406f69836

I think it has something to do with send_file not adhering to the
Content-Range headers. I'd appreciate any insight into this problem.
I feel like I'm so close because it pretty much all works, except for
seeking near the beginning causing a new request.

Thanks!