Specially-commissioned "silent" fireworks are to be used for the first time at the traditional Princes Street Gardens event this Sunday.

Organisers of the Fireworks Concert say they will be timed to complement quieter passages of music.

Up to 250,000 spectators are expected to watch the spectacular finale to the festival season from around the city.

Fifteen technicians have spent the past week setting up around 100,000 fireworks at the Castle, and conducting numerous safety checks.

Nine-year-old Morgan Bevin, from Livingston, will be pressing the button to start the display at 9pm, after winning a Radio Forth competition.

Keith Webb, director of the international company Pyrovision, has been working on setting the fireworks to the music for the past six months.

But while the rest of the city enjoys the results, he will be in a stone bunker in Edinburgh Castle, masterminding the display.

He said: "We're using these silent fireworks for the first time in a major display.

"This is the most important display we do in this country, so it's a good chance to showcase new material.

"If there's a quiet passage of music, it seems a bit pointless to shoot lots of noisy fireworks up in the sky. So instead we will have these very soft fireworks lighting up the sky when the violins come in.

"The music is very bubbly, with lots of stops and starts. We're trying to use fireworks to highlight individual notes.

"It's a very precise question of timing. It might take two to six seconds for a shell to burst in the sky, so we have to work out exactly when to set it off."

He will be spending Saturday and Sunday attending rehearsals with the Scottish Chamber Orchestra, to help fine-tune the display.

The team from Pyrovision have already spent a day-and-a-half checking every cable connected to the fireworks, to ensure that everything goes according to plan.

They are using 12 tonnes of equipment in total, which has been brought to Edinburgh in a fleet of six lorries. The drivers all have special licences in line with UN safety regulations.

Mr Webb, who has 27 years' experience working on the festival finale, said: "I've been thinking about this since February. I tend to sit down and listen to the music 100 times until it's embedded in my head.

"It's very fulfilling when you see people enjoying it. But, one day, it would be nice to actually get to see the display ourselves."

The Bank of Scotland Fireworks Concert, which starts at 9pm, will be conducted by Romanian-born Nicolae Moldoveanu for the second time.

This year's programme includes the swirling rhythms of eastern European folk music, with excerpts from Brahms' Hungarian Dances and Dvorák's Slavonic Dances.

People without tickets can enjoy a live broadcast on a big screen in Inverleith Park, with a viewing area particularly well-suited to families with young children.