To use this buildpack, you should prepare a .buildpacks file that contains this buildpack url and your real buildpack url:
$ ls .buildpacks ... $ cat .buildpacks https://github.com/soomo/heroku-buildpack-audiowaveform $ heroku create --buildpack https://github.com/ddollar/heroku-buildpack-multi $ git push heroku master ...
You can verify that sox is installed by calling:
$ heroku run "audiowaveform"
Copy the snippet above into CLI.