Is it possible to combine spells?

Question

Slightly related to the "What spell inflates Aunt Marge?" question.
Can spells be combined to create the effect of casting two spells (but without the time lag involved in pronouncing a long name and doing the "swish and flick" gesture twice)?
Would this be creating a new spell?

Does anyone remember anything in the books that could possibly be ascribed to a character performing two spells together? (Not two characters aiming different spells at the same target at the same time.)

[Slightly off on a tangent too, but would it be possible for a wizard to use two wands at the same time?]

Answer 1

• Can spells be combined to create the effect of casting two spells (but without the time lag involved in pronouncing a long name and doing the "swish and flick" gesture twice)? Would this be creating a new spell?

I'm not sure if you want to count it, but Bat-Bogey Hex seems to fit the bill. It does 3 spells at once: Turns someone's bogeys into bats (some sort of transfiguration spell); causes the bats to be enlarged (effect of Engorgio); and sets them attacking the target (effect of Oppugno).

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• would it be possible for a wizard to use two wands at the same time

Yes, though the example was NOT not to fire off two different spells. From DH, CH 23:

As Ron ran to pull Hermione out of the wreckage, Harry took the chance: He leapt over an armchair and wrested the three wands from Draco’s grip, pointed all of them at Greyback, and yelled, “Stupefy!” The werewolf was lifted off his feet by the triple spell, flew up to the ceiling and then smashed to the ground.