This month’s release of ”Lord of the Rings: The Two Towers” puts us in the middle not only of the Tolkien trilogy but also of a bold development in filmmaking and marketing — simultaneously made sequels. With ”L.O.T.R.,” New Line Cinema took perhaps the biggest movie gamble of all time: three installments shot at once (over a grueling 15-month period in New Zealand) at a cost of nearly $300 million. It may sound crazy, risking mammoth outlays on sequels without even knowing if the first movie will fly or flop. But the studios think they’re onto something. Even now, Warner Brothers is in postproduction with two ”Matrix” sequels, set for May and December 2003. And the studio already has ”Harry Potter” installments scheduled through 2005.

Simulsequeling answers the daunting economics of traditional sequels. There are actors’ escalating demands: Mike Myers took home $3 million for ”Austin Powers,” almost $10 million for ”The Spy Who Shagged Me” and $25 million for ”Goldmember”; Jodie Foster, who reportedly got $1 million for ”The Silence of the Lambs,” is said to have wanted $20 million for ”Hannibal,” forcing Dino de Laurentiis to settle for Julianne Moore. Then there’s production cost. New Line estimated that making the Tolkien trilogy piece by piece could be nearly twice as costly as doing it in one go. If you have Middle-earth to build, why pay for it three times?

It’s a gamble (you could be cloning ”Ishtar”), but Hollywood sees big franchise films as good simulsequeling bets.