Created attachment 150285 [details]
patch for head/sys/tools/feeder_eq_mkfilter.awk
The sound mega-commit in 2009 (193640) introduced a parametric software equalizer, with the ability to customize its parameters at compile time using FEEDER_EQ_PRESETS in make.conf(5).
I believe the only documentation on the format of this is referenced in ariff's commit comment: http://people.freebsd.org/~ariff/SOUND_4.TXT.html
Going by that description of FEEDER_EQ_PRESETS, the build system parses it slightly incorrectly. I believe that the parsing tool is unchanged since its original introduction, so the attached patch should apply for all versions.