#!/bin/bash

cd /pub/multimedia/audio/music/by-artist
for ALBUM_DIR in */*/; do
    echo -n "$ALBUM_DIR ..."
    MAX_TS=$(find "$ALBUM_DIR" -name '*.mp3' -exec stat -c %Y {} \; | sort -rn | head -1)
    touch -t $(date -d@$MAX_TS +%Y%m%d%H%M.%S) "$ALBUM_DIR"
    echo
done