Last year was the first time Windsor Castle hosted the event
The second ever Royal Tattoo at Windsor Castle will get under way later with the biggest public display of military musicians for "many years".
The four-day event will feature 500 musicians from all three armed services as well as a number of displays.
Last year's inaugural event attracted 18,000 people with facilities prepared for up to 30,000 visitors this year.
The event is supporting the Royal British Legion with profits going to help those serving on operations.
Promoters claim the event, which runs until Saturday, will involve the largest number of military musicians to perform in public for many years.
Mounted displays will also feature 250 horses during the event.
Brigadier Melville Jameson, producer of the Royal Tattoo, said: "This year's programme is looking really exciting with a stunning line-up of talent.
"For the finale, the vast Combined Massed Bands will be joined by the Massed Pipes and Drums to create a splendid vision and incredible sound, which coupled with the rest of the strong cast, will make it a night to remember."