Tens of thousands of Festival revellers are expected to converge on one of Edinburgh's historic town squares tonight for a sound and light show which marks the 70th anniversary of the world famous event.

Bloom, a free event sponsored by Standard Life, is to run over two nights this weekend in St Andrew Square in the New Town.

It will see spectacular visuals along with newly composed music shown over three sides of the square.

Beginning at 10pm, audiences will not see a narrative displayed from beginning to end, but are being invited to walk around the square as the ever-changing light show is transmitted onto the faces of the buildings for two hours.

Free tickets have been taken up by people who will guarantee access from 10pm, but from 10.30pm access is open on a first come, first served basis.

It is the third opening event of light and music since the arrival of festival director Fergus Linehan, who said the event is a "moment to celebrate."

Once again the award winning production company 59 Productions have created the event, as they did with 2016's Deep Time.

More than 50 projectors have been installed around the square to show the images, which give an artistic history of the city, and the festival, since the late 1940s.

Fergus Linehan, director of the Edinburgh International Festival (EIF), said: "It being the 70th anniversary we wanted to do something far more inclusive, and we know there are tens of thousands of people keen to come along, so we thought how do we do this in a way to facilitate everyone from families of people to people in a show, and a much wider audience.

"We wanted to do it over a much longer period of time, and over two nights instead of one.

"So we needed a much bigger site, a lot more equipment, and obviously a much bigger budget."

He said the event has more "generosity and inclusion" than the previous opening events.

Because of the scale, Mr Linehan said he was grateful the event has been backed by Standard Life and the Scottish Government's Expo Fund.

The visual spectacle will be accompanied by a soundscape by composer and musician Nick Powell who among his extensive theatre credits has written the score for many popular shows at the International Festival in the past including Lanark and The Wonderful World of Dissocia.