Anna Kendrick found 'Perfect Pitch' "challenging".
The 'Up in the Air' actress found it hard to keep up when filming the musical movie, especially a scene which sees two rival acapella groups - one all girls and the other all boys - battle it out in a campus competition.
She said: "It definitely was challenging. The scene in the riff-off when there's, like, four different groups and we're all jumping in ... there were so many moving parts and it was so hard to keep track of what we were doing, where we were in the scene, and to try and have this kind of flirty, semi-romantic through-line with Jesse [Skylar Astin] through that scene."
The 27-year-old star has already had experience in musicals, with her first ever acting role being Dinah in Broadway's 'High Society' when she was just 12, but she praised 'Perfect Pitch' director Jason Moore for helping the cast find their feet.
She added to BuzzineFilm.com: "It was great to have somebody like Jason Moore, who directed 'Avenue Q', as the captain of the ship, because he comes from a musical background and he definitely has a film director's mind as well.
"We definitely relied on him a lot to make sure that all those moving parts were gelling and we were headed in the right direction."
Anna plays university freshman Beca, who joins her school's all-girl acapella group The Bellas to help them take on boy band Treble Makers in a campus competition. The groups perform songs such as Kelly Clarkson's 'Since U Been Gone' and 'Don't You (Forget About Me)' by Simple Minds.
'Pitch Perfect' is set to be released in the UK in December.