remains—the best-selling album of all time, with sales estimated by various sources as somewhere between 65 and 110 million copies worldwide. His 1987 album Bad sold over 45 million copies and became the first album to have five number-one singles chart on the Billboard Hot 100. Jackson had the most number-one singles throughout the decade (9), and spent the most weeks at number one (27 weeks). His 1987 Bad World Tour grossed over $125 million worldwide, making it the highest grossing world tour by a solo artist during the decade. Jackson earned numerous awards and titles during the 1980s, the most notable of which were a record eight Grammy Awards and eight American Music Awards in 1984, and the honor of "Artist of the Decade" by U.S. President George H.W. Bush. Jackson was arguably the biggest star during this time, and would eventually sell more than one billion records around the world. Prince was a popular star of the 1980s and the most successful chart act of the decade. His breakthrough album 1999, released in 1982, produced three top-ten hits and the album itself charted at number nine on the Billboard 200. His sixth studio album Purple Rain was an international success, boosting Prince to superstardom and selling over 25 million copies worldwide. The album produced the US number-one singles, "When Doves Cry" and "Let's Go Crazy" and sold 13 million copies in the U.S. as of 1996. Prince released an album every year for the rest of the decade, all charting within the top ten, with the exception of Lovesexy. In the 1990s, he infamously changed his name to an unpronounceable symbol in response to a record dispute with Warner Brothers. He went on to sell over 120 million records worldwide and win seven Grammy Awards. Madonna and Whitney Houston were groundbreaking female artists of the decade. The keyboard synthesizer and drum machine were among the most popular instruments in music during the 1980s, especially in new wave music. After the 1980s, electronic instruments continued to be the main component of mainstream pop. Hard rock, heavy metal, and glam metal became some of the most dominant music genres of the decade, peaking with the arrival of such bands as Mötley Crüe, Guns N' Roses, Metallica, Iron Maiden, Bon Jovi, Def Leppard, Poison, Europe, Megadeth, Slayer, Anthrax, and virtuoso guitarists such as Joe Satriani and Yngwie Malmsteen. The scene also