Composer Mira Calix with the art installation at Fairlop Waters

The hill of Fairlop Waters is alive with the sound of music.

The final touches are put on the musical sculpture at Fairlop Waters

If you’re walking in the country park this summer and as if from nowhere you start to hear a musical score, strange melodies and even a full voice choir, never fear.

The waves of sound are very real and come from a stone sculpture, or “monolithic” art installation, set up at the top of the park’s hill to celebrate London in its Olympic year.

Dreamed up by musician Mira Calix and built out of gneiss rock with the help of mineralogists from the Natural History Museum, the approximately four metres tall installation is known as Nothing Is Set In Stone.

It is one of a series of free cultural events called Secrets: Hidden London, which form part of the London 2012 Festival supported by the Mayor of London and Redbridge Vision.

Made from thousands of stones built around a larger central stone and containing hidden speakers and sensors, from Thursday visitors will trigger it to play music and human song which is pushed out through the rock.

Mira, who has released electronica albums and composed for the London Sinfonietta and the Royal Shakespeare Company, offered some explanation while setting it up with her team.

She said: “It reacts to who is there, if nobody is there it doesn’t sing, once someone arrives it reacts to them.

“You have to move around it and discover it. It’s up to who is there to play with it and figure it out.”

Using customised software, it offers music composed by Mira based on the four elements and includes the voices of the University of Johannesburg’s choir.

Mira joked: “It won’t play Heart FM unfortunately.

“It’s a mixture of natural sounds.

“It gives the impression that the whole thing is on fire or that there’s water running through it.”

Mira said she quickly picked Fairlop Waters as a location as it seemed “absolutely perfect”.

The sculpture will be in place at the country park off Forest Road, Barkingside until September and Mira will return regularly to see how people react to the stone, and vice versa.