The new flac frontend has a "Replaygain" option enabled by default.
Kinda foolish to have this on by default if it butchers the sound like
this. I can understanding the need to normalize when batch encoding
but on a per-album basis and file basis rather silly.
--replay-gain Calculate ReplayGain values and store in Vorbis
comments. Title gains/peaks will be computed
for each file, and an album gain/peak will be
computed for all files. All input files must
have the same resolution, sample rate, and
number of channels. The sample rate must be
one of 8, 11.025, 12, 16, 22.05, 24, 32, 44.1,
or 48 kHz. NOTE: this option may also leave a
few extra bytes in the PADDING block.