I've done:

  sox piano.flac piano.wav
  gzip -c < piano.wav > piano.wav.gz
  brotli-encode < piano.wav > piano.wav.brotli
  ls -l piano2.wav piano2.wav.gz piano2.wav.brotli piano2.flac

and gotten:

  -rw-r--r-- 1 robryk users 40056 Jun 14 19:15 piano2.wav.gz
  -rw-r--r-- 1 robryk users 87656 Jun 14 19:13 piano2.wav
  -rw-r--r-- 1 robryk users 34221 Jun 14 19:14 piano2.wav.brotli
  -rw-r--r-- 1 robryk users 52372 Jun 14 19:13 piano2.flac

Either I'm doing something wrong or even plain gzip fares better than flac (edit: in this particular case, obviously). brotli-encode compresses using brotli[1] using the font mode.

[1] https://code.google.com/p/font-compression-reference/source/...