copy_files_enumerated.sh

# length of maximum digit to enumerate song list
function get_digit_length() {
    list=("$@")
    length="${#list[@]}"
    ((length++))
    length="${#length}"
    echo "$length"
}
# pad with 0's in front. the number of zeros
# is represented by the second parameter
function get_formatted_index() {
    index="$1"
    repl="%0$2"d
    printf -v num $repl $index;
    echo $num;
}
# enumerate the song list and copy song with enumeration as name
function rename_files() {
    ext="$1"
    shift
    fileList=("$@")
    length="$(get_digit_length ${fileList[@]})"
    # store the new files
    newPath="./new"
    mkdir -p $newPath
    # copy the files to the new directory
    index=1
    for song in "${fileList[@]}"; do
        newName="$(get_formatted_index $index $length)"
        newName="$newName.$ext"
        echo "Copying $song to $newPath/$newName"
        cp $song $newPath/$newName
        ((index++));
    done
}

newSongList=(
)
## TODO: get each line from a pipe via xargs.
##
rename_files "mp3" "${newSongList[@]}"

Mainly a practice in copying from terminal.
:set mouse=
seems to enable OS Selection of text directly..