MIDI to WAV / WavPack. For extreme high audio quality, we use 64bit/32bit floating-point intermediate file.

midi_to_wav.sh

#!/bin/bash

BANKSELECT='gm'

SF="$HOME/Timbres Of Heaven GM_GS_XG_SFX V 3.2 Final.sf2"
find "$1" -type f -iname "*.mid" -print0 | while IFS= read -r -d '' fullfile; do
  file=`basename ${fullfile}`
  fluidsynth -g 0.01 -o synth.midi-bank-select=$BANKSELECT -o synth.midi-channels=256 -o synth.polyphony=4096 -r 48000 -O double -F "${file}_raw.wav" "${SF}" "${fullfile}"
  sox --norm=-1 "${file}_raw.wav" -b 32 -e signed-integer "${file}.wav"
  rm "${file}_raw.wav" &
  wavpack -q -f -x6 -m -d "${file}.wav" &
done