Apply playback tempo filter to mp3
#!/usr/local/bin/bash
# convert.sh
# Apply tempo filter to .mp3 files in this and all sub directories
# Optional: Delete original file after conversion
shopt -s globstar
i=1
for song in ./**/*.mp3
do
ffmpeg -i "$song" -filter:a "atempo=2.0" -vn $i.mp3
i=$((i+1))
done