def update_to_v23(self):
        """Convert older (and newer) tags into an ID3v2.3 tag.

        This updates incompatible ID3v2 frames to ID3v2.3 ones. If you
        intend to save tags as ID3v2.3, you must call this function
        at some point.

        If you want to to go off spec and include some v2.4 frames
        in v2.3, remove them before calling this and add them back afterwards.
        """

        self.__update_common()

        # we could downgrade unknown v2.4 frames here, but given that
        # the main reason to save v2.3 is compatibility and this
        # might increase the chance of some parser breaking.. better not

        # TMCL, TIPL -> TIPL
        if "TIPL" in self or "TMCL" in self:
            people = []
            if "TIPL" in self:
                f = self.pop("TIPL")
                people.extend(f.people)
            if "TMCL" in self:
                f = self.pop("TMCL")
                people.extend(f.people)
            if "IPLS" not in self:
                self.add(IPLS(encoding=f.encoding, people=people))

        # TDOR -> TORY
        if "TDOR" in self:
            f = self.pop("TDOR")
            if f.text:
                d = f.text[0]
                if d.year and "TORY" not in self:
                    self.add(TORY(encoding=f.encoding, text="%04d" % d.year))

        # TDRC -> TYER, TDAT, TIME
        if "TDRC" in self:
            f = self.pop("TDRC")
            if f.text:
                d = f.text[0]
                if d.year and "TYER" not in self:
                    self.add(TYER(encoding=f.encoding, text="%04d" % d.year))
                if d.month and d.day and "TDAT" not in self:
                    self.add(TDAT(encoding=f.encoding,
                                  text="%02d%02d" % (d.day, d.month)))
                if d.hour and d.minute and "TIME" not in self:
                    self.add(TIME(encoding=f.encoding,
                                  text="%02d%02d" % (d.hour, d.minute)))

        # New frames added in v2.4
        v24_frames = [
            'ASPI', 'EQU2', 'RVA2', 'SEEK', 'SIGN', 'TDEN', 'TDOR',
            'TDRC', 'TDRL', 'TDTG', 'TIPL', 'TMCL', 'TMOO', 'TPRO',
            'TSOA', 'TSOP', 'TSOT', 'TSST',
        ]

        for key in v24_frames:
            if key in self:
                del(self[key])
Convert older (and newer) tags into an ID3v2.3 tag.

        This updates incompatible ID3v2 frames to ID3v2.3 ones. If you
        intend to save tags as ID3v2.3, you must call this function
        at some point.

        If you want to to go off spec and include some v2.4 frames
        in v2.3, remove them before calling this and add them back afterwards.