FreeBSD Thinkpad Volume up/down in X

$ uname -a
FreeBSD lent.shxd.cx 11.0-CURRENT FreeBSD 11.0-CURRENT #0 r293338: Wed Jan 13 21:26:36 PST 2016     root@lent.shxd.cx:/usr/obj/home/dteske/src/freebsd_svn/base/head/sys/GENERIC  amd64
$ pkg install -y xbindkeys
# ...

Add "xbindkeys" on a line by itself to your ~/.xinitrc file:

Add the following to (or use the following for) ~/.xbindkeys file:
=== BEGIN FILE ===
# Decrease volume
"mixer vol -5:-5"
	XF86AudioLowerVolume

# Increase volume
"mixer vol +5:+5"
	XF86AudioRaiseVolume
=== END FILE ===

If you install misc/xosd from ports and osd_mixer from http://pastebin.com/xqkTrjcv
you can instead use the following which will give you an on-screen display of volume level:
=== BEGIN ALTERNATE ~/.xbindkeys FILE ===
# Decrease volume (visually)
"osd_mixer vol -5:-5"
	XF86AudioLowerVolume

# Increase volume (visually)
"osd_mixer vol -5:-5"
	XF86AudioRaiseVolume
=== END FILE ===