Saoirse Ronan has thrown herself into piano lessons to portray a vampire musician in upcoming movie Byzantium.

The teenage actress stunned director Neil Jordan after mastering a complicated piano piece in just 12 weeks.

Jordan had planned to film Ronan miming a performance of Beethoven's Piano Sonata No. 3 but the determined star began practising two hours a day to learn the classical work in its entirety.

Ronan explains, "There's this scene in the film where my vampire character sits down to play an old piano and entrances everyone with her playing. My vampire Eleanor is 200 years old in the film and had been playing piano that long, so there was a bit of pressure but I wanted it to look real."

The 17 year old's music teacher Yvonne Collier is amazed with her progress and hopes she will continue to study the piano.

Collier tells the Irish Independent, "I started teaching Saoirse the piano with little exercises so she could learn the notes. Then we did lots of Lady Gaga pieces before moving on to Beethoven. Since her very first piano lesson it is truly remarkable what Saoirse can now do on the piano.

"The E minor middle section of the piece involves the left hand crossing over the right; a technique very difficult to master even with years of experience but one that Saoirse has mastered within a few weeks. She can master anything she puts her mind to."