PiCore 13.x Sox 14.4.2+git20190427:

Based on:
http://tinycorelinux.net/10.x/x86_64/tcz/src/sox/sox.tcz.build-dep

Downloaded latest "orig" source archive from Debian package repo:
http://deb.debian.org/debian/pool/main/s/sox/sox_14.4.2+git20190427.orig.tar.bz2

* Install extensions:  compiletc squashfs-tools libtool-dev alsa libasound-dev
* export CFLAGS="-march=armv6 -mfpu=vfp -mfloat-abi=hard -Os -pipe" CXXFLAGS="-march=armv6 -mfpu=vfp -mfloat-abi=hard -Os -pipe -fno-exceptions -fno-rtti" LDFLAGS="-Wl,-O1"
* ./configure --prefix=/usr/local --disable-static --with-distro=PiCore

BUILD OPTIONS
Debugging build............no
Distro name ...............PiCore
Dynamic loading support....yes
Pkg-config location........$(libdir)/pkgconfig
Play and rec symlinks......yes
Symlinks enabled...........yes

OPTIONAL DEVICE DRIVERS
ao (Xiph)..................no
alsa (Linux)...............yes
coreaudio (Mac OS X).......no
sndio (OpenBSD)............no
oss........................yes
pulseaudio.................no
sunaudio...................no
waveaudio (MS-Windows).....no

OPTIONAL FILE FORMATS
amrnb......................no
amrwb......................no
flac.......................no
gsm........................yes (in-tree)
lpc10......................yes (in-tree)
mp2/mp3....................no
 id3tag....................no
 lame......................no
 mad.......................no
 twolame...................no
oggvorbis..................no
opus.......................no
sndfile....................no
wavpack....................no

OTHER OPTIONS
ladspa effects.............yes
magic support..............no
png support................no
OpenMP support.............yes, -fopenmp

* make

* sudo make DESTDIR=/tmp/sox install-strip
* split /tmp/sox into directories:  sox sox-doc sox-dev

* sudo chown -R root:root sox*
* In each dir. run "find usr ! -type d | sed "s/^/\//g" > ../sox.tcz.list".
 - for dir in `find -maxdepth 1 -mindepth 1 -type d`; do cd $dir; find usr ! -type d | sed "s/^/\//g" > ../$dir.tcz.list; cd ..; done
* Make into extensions using mksquashfs. "mksquashfs sox sox.tcz
  "md5sum sox.tcz > sox.tcz.md5.txt" etc...
 - for dir in `find -maxdepth 1 -mindepth 1 -type d`; do mksquashfs $dir ${dir#./}.tcz; md5sum ${dir#./}.tcz > ${dir#./}.tcz.md5.txt; done
* Make sox.tcz.dep:

Deps:
sox.tcz.dep:
 libasound.tcz
 gcc_libs.tcz
 libltdl.tcz

sox-dev.tcz.dep:
 sox.tcz

* Copy sox.tcz (+ dep, md5) to "tce/optional".
* tce-load -i sox