Prepare random sets of Make Noise Morphagene reels for copying to SD card

select-random-reels.sh

#!/bin/bash

### given a folder full of Morphagene-suitable audio files, select 32
### at random and make a directory full of hardlinks(!!) to them, ready
### for copying to an SD card. Also generates an index file so you can
### trace back to the original filenames.

# macOS and GNU both seem to have sort -R for randomizing. You may need to
# adjust if using some other implementation

REELS_HOME="$HOME/Documents/Audio/reels"
if [ "$1" != "" ] ; then
  REELS_HOME="$1"
fi

_die() {
  echo "select-random-reels.sh: FATAL: $*" >&2
  exit 1
}

cd "$REELS_HOME" || _die "can't access reels: $REELS_HOME"

# the final 'sort' is intended to ensure any related reels in the selection
# are adjacent
selected="$(
  find . -type f -name '*.wav' -maxdepth 1 ! -name 'mg[1-9a-w].wav' \
  | sort -R \
  | head -32 \
  | xargs -n1 basename \
  | sort -n \
)"
digest="$(echo "$selected" | openssl sha)"

# from Morphagene user manual; colours repeat in this order, except white
# which is prepended to keep the modulus indexing uncomplicated
declare -a reelcolours
reelcolours[0]=white
reelcolours[1]=blue
reelcolours[2]=eucalypt
reelcolours[3]=green
reelcolours[4]=yellow
reelcolours[5]=orange
reelcolours[6]=red
reelcolours[7]=violet
reelcolours[8]=white

# Morphagene reel filenames are mg1.wav thru mg9.wav and mga.wav thru mgw.wav
# pregenerate the names
declare -a reelnames
n=1
for id in {1..9} {a..w} ; do
  reelnames[$n]="mg${id}.wav"
  n=$((n+1))
done

n=1
mkdir "$digest" || _die "can't make reelset directory: $digest"
cd "$digest"    || _die "can't access reelset directory: $digest"
{ echo "# random reelset: $digest"; echo; } >> INDEX.md
{
  echo 'COLOUR NAME ORIGINAL-NAME'
  for reel in $selected ; do
    mgn="${reelnames[$n]}"
    colourindex=$(((n+8) % 8))
    echo "${reelcolours[$colourindex]}" "$mgn" "$reel"
    ln "../$reel" "$mgn"
    n=$((n+1))
  done
} | column -t >> INDEX.md

echo "your new reel selection: $digest"

comment here if you have a better name than eucalypt for the first green in the reel colour sequence :-/