# For an output like this
  # 00:07:22 first.mp3
  # 00:02:33 second.mp3
  # 00:04:04 third.mp3

# Use this
for file in *.mp3
do
  echo -n $(ffprobe $file 2>&1 | grep 'Duration' | cut -d',' -f1 | cut -d' ' -f4 | cut -d'.' -f1)
  echo " $file"
done