An undiscovered piece of music written by Wolfgang Amadeus Mozart when he was a young teenager has been found at a library in Germany. 

It is believed the piece - titled Serenade in C - was composed in the mid to late 1760s.

| The manuscript, which is believed to have been created in 1780. Pic: Leipzig Municipal Libraries

It consists of seven miniature movements for a string trio lasting about 12 minutes, the Leipzig Municipal Libraries said in a statement.

Researchers discovered the manuscript at the city's music library while compiling the latest edition of the Kochel catalogue, the archive of Mozart's musical works.

The unsigned manuscript was not written by Mozart himself but is believed to be a copy made around 1780. It consists of dark brown ink on medium-white handmade paper and the parts are individually bound.

The music will be performed at the Leipzig Opera on Saturday after it was debuted on Thursday at the launch of the new Kochel catalogue in Salzburg.

Born in 1756, Mozart was considered a child prodigy and began composing at five years old.

Despite his death aged 35, he is considered one of the greatest composers in history, and created more than 800 works in his lifetime.

You can listen to the full piece here at 1:25:40.