With North America readying for a major solar eclipse, Ozzy Osbourne will celebrate the exact moment by singing "Bark at the Moon" as the sun disappears.
Moonstock, a new metal festival in Illinois, will take place over four days culminating on August 21 with the US-wide eclipse.
Osbourne will take the stage at 1:20 (1820 GMT) and start his set with "Bark at the Moon," his 1983 song about the wrath of a werewolf-like monster.
The 68-year-old metal legend will need to be punctual as the total eclipse will last two minutes and 29 seconds. The song runs four minutes and 16 seconds on his album by the same name.
The festival, which recommends that fans wear protective eyewear, will take place at a vineyard near De Soto, Illinois, about 140 kilometers (85 miles) southeast of St. Louis -- within the region that will have the best visibility of the eclipse if the weather permits.
The solar eclipse -- when the Moon blocks the Sun as it passes between the vital star and Earth -- will be the first to be visible across the entire United States since 1918, according to NASA.
The eclipse will be at least partially visible in all 50 states including Hawaii as well as in Canada.
Osbourne, with lyricism that dabbles in the occult and infamous on-stage gestures such as biting the head off a bat, is one of the pioneers of heavy metal.
His band Black Sabbath in February played what it said would be its last-ever concert in its native Birmingham, England, but Osbourne has several solo shows ahead.
Other bands to play the Moonstock festival include Papa Roach, one of the leading "nu metal" bands of the 1990s.