(1)    Except to the extent that the corporation‘s articles of incorporation are amended to provide that the voting requirements of s. 180.1003 (3), 180.11032 (3), 180.1202 (3), 180.1402 (3) or 180.1404 (2) apply, subs. (2) and (3) govern the shareholder vote required on a proposal concerning a subject covered by s. 180.1003 (3), 180.11032 (3), 180.1202 (3), 180.1402 (3) or 180.1404 (2) if the corporation was organized before January 1, 1973, and has not expressly elected, before January 1, 1991, majority or greater affirmative voting requirements under s. 180.25 (2) (a), 1987 stats., with respect to the subject matter of the proposal.

   (2)   Except as provided in sub. (3), in lieu of the vote required by s. 180.1003 (3), 180.11032 (3), 180.1202 (3), 180.1402 (3) or 180.1404 (2), whichever is applicable to the subject matter of a proposal, a proposal described in sub. (1) must be approved as follows:

      (a)    By the affirmative vote of the holders of two-thirds of the shares entitled to vote on the proposal, unless par. (b) applies.

      (b)    If any class or series of shares is entitled to vote on the proposal as a class, by the affirmative vote of all of the following:

         1.    The holders of two-thirds of the shares of each class of shares and of each series entitled to vote as a class.

         2.    The holders of two-thirds of the total shares entitled to vote on the proposal.

   (3)   Whenever, with respect to a proposal described in sub. (1), the articles of incorporation require the vote or concurrence of the holders of a greater proportion of the shares, or of any class or series of shares, than is required by sub. (2), the provisions of the articles of incorporation shall control.

   (4)   If a corporation has a bylaw in effect on December 31, 1990, that establishes a greater shareholder voting requirement than one required under this chapter, that voting requirement applies until the bylaw is amended or repealed.