assert isinstance(song, URIRef), "songInMpd now takes URIRefs"

    mpdHome = None

    for line in open(path.expanduser("~/.mpdconf")):

        if line.startswith("music_directory"):

            mpdHome = line.split()[1].strip('"')

    if mpdHome is None:

        raise ValueError("can't find music_directory in your ~/.mpdconf")

    mpdHome = mpdHome.rstrip(path.sep) + path.sep

    songFullPath = songOnDisk(song)

    if not songFullPath.startswith(mpdHome):

        raise ValueError("the song path %r is not under your MPD music_directory (%r)" % (songFullPath, mpdHome))

    mpdRelativePath = songFullPath[len(mpdHome):]

    if path.join(mpdHome, mpdRelativePath) != songFullPath:

        raise ValueError("%r + %r doesn't make the songpath %r" % (mpdHome, mpdRelativePath, songFullPath))

    return mpdRelativePath.encode('ascii')

def songOnDisk(song):

    graph = getGraph()

    songFullPath = path.join(root(), graph.value(song, L9['showPath']))

    return songFullPath