The Morton H. Meyerson Symphony Center opened its doors in September 1989 -- seems like only 18 years ago. Accordingly, there are big doings at I.M. Pei's palace on September 27 -- a free open house that'll include the intriguingly advertised "instrument petting zoo." And if you've got a few spare moments, Meyerson's 2MCompanies Inc. just posted Part One of a making-of doc, and it's quite the revealing flashback from the man who says toward the end that "I'm really not a public person" when explaining his reluctance to let H. Ross Perot bestow upon the joint Meyerson's name. I'll post Part Two when it becomes available.