Amanda Seyfried will sing in 'Ted 2'.

The 'Million Ways to Die in the West' actress has impressed her co-star and writer Seth Macfarlane with her ''beautiful'' singing voice so he wrote a special medley for her to perform in the comedy sequel.

Seth said: ''She's going to sing in 'Ted 2'. She has a beautiful voice.''

Amanda added: ''He wrote a nice medley, a Ted-ley, but I don't know if I'm up to speed yet.''

While Amanda is comfortable singing on camera, one thing she is relieved she won't have to do is master a Boston accent for the role.

Asked during an interview to mimic one of the characters from 'Family Guy', another of Seth's creations, she said: ''I can't, I can't do a Boston accent.''

Seth exclaimed in response: ''You can't do a Boston accent? But you're starring in 'Ted 2'!''

Amanda replied: ''You said I didn't have to do that, like, weeks ago. God, if you want me to do a Boston accent, I gotta... I would never embarrass myself in front of him by trying to do his voices.''