While Forum's music isn't challenging, it's the book that can be tough sometimes. Of course, if you're working with wonderful comedic actors, then it's not extremely challenging and your performance will almost certainly be great. However, there are people out there, be they inexperienced or simply not particularly talented, that have NO comedic timing. If you're putting on Forum with a cast that doesn't have flawless timing, this is where challenges will present themself. If the timing and body language aren't practically flawless, this is where you'll run into problems. Hope that helped
