An orchestra is a large instrumental ensemble that contains sections of string, brass, woodwind, and percussion instruments. The term orchestra derives from the Greek ορχήστρα, the name for the area in front of an ancient Greek stage reserved for the Greek chorus. The orchestra grew by accretion throughout the 18th and 19th centuries, but changed very little in composition during the course of the 20th century.

A smaller-sized orchestra for this time period (of about fifty players or fewer) is called a chamber orchestra. A full-size orchestra (about 100 players) may sometimes be called a "symphony orchestra" or "philharmonic orchestra"; these modifiers do not necessarily indicate any strict difference in either the instrumental constitution or role of the orchestra, but can be useful to distinguish different ensembles based in the same city (for instance, the London Symphony Orchestra and the London Philharmonic Orchestra). A symphony orchestra will usually have over eighty musicians on its roster, in some cases over a hundred, but the actual number of musicians employed in a particular performance may vary according to the work being played and the size of the venue. A leading chamber orchestra might employ as many as fifty musicians; some are much smaller than that. Orchestras can also be found in schools. The term concert orchestra may sometimes be used (e.g., BBC Concert Orchestra; RTÉ Concert Orchestra)—no distinction is made on size of orchestra by use of this term, although their use is generally distinguished as for live concert. As such they are commonly chamber orchestras.

Katheryn Elizabeth Hudson (born October 25, 1984), known by her stage name Katy Perry, is an American singer, songwriter and actress. Perry grew up with gospel music, and during her first year of high school she pursued a music career as Katy Hudson, releasing her first studio album called Katy Hudson which failed to chart. She recorded a solo album later, which was never released. After signing with Capitol Music Group in 2007, her fourth record label in seven years, she adopted the stage name Katy Perry.

She first gained recognition with the release of her first mainstream album, One of the Boys in 2008, which spawned three Billboard Hot 100 top-ten songs—"I Kissed A Girl", "Hot n Cold" and "Waking Up In Vegas". Perry supported the album with her Hello Katy Tour. In 2010, her third studio album, Teenage Dream (2010), which topped the Billboard 200 chart, and spawned five number one singles—"California Gurls", "Teenage Dream", "Firework", "E.T." and "Last Friday Night (T.G.I.F.)"—Teenage Dream was the only album (after Michael Jackson's Bad)—to do so, and the first female in history to achieve this milestone. She embarked on the California Dreams Tour, which grossed nearly $60 million worldwide. Perry re-released the album under the name of Teenage Dream: The Complete Confection on March 26, 2012, and the re-release has already spawned the number-one single "Part of Me".

Walt Ribeiro, a New Jersey native, is a composer of classical music. His work has been primarily distributed via the internet. His symphony I.I was written for an 80-piece orchestra, but produced using orchestral sampling software. Ribeiro is also notable for his music tutorials available via web sites such as YouTube, which he ended in October 2009. That same year he launched For Orchestra where he arranged pop songs for orchestra. His arrangements have covered songs by Lady Gaga, Radiohead, Pearl Jam, Rimsky Korsakov, and MGMT to name a few. It has since been featured on Comedy Central Tosh.O,Perez Hilton, Green Plastic for his Radiohead arrangement and more.

Ribeiro was born January 25, 1984.

Lindsey Stirling (born on September 21, 1986) is an American violinist, musician, dancer, performance artist, and composer. In 2010 she competed on the fifth season of America's Got Talent. Stirling is noted for her versatility performing music from country to hip hop.

At the age of 23 Stirling was a quarter-finalist on the fifth season of America's Got Talent where she was known as the ‘Hip Hop Violinist’. After Stirling's performance, Sharon Osbourne said, "Wow... we love you Lindsey!” and Piers Morgan called her performance "Electrifying!".

At the age of 5, after being influenced by the classic music records played by her father, Stirling requested the opportunity to learn and play the violin.

Stirling was classically trained through private lessons for 12 years. When she was 16, she joined a rock band with four friends called Stomp on Melvin. As part of her experience with Stomp on Melvin, Stirling wrote a solo violin rock song, and her performance helped her to win both the title of Arizona’s Jr. Miss in 2005 and the talent category of the National Jr. Miss Pageant. As of May 2, 2012, Stirling is 5'3" tall.

Bernard Johan Herman Haitink, CH, KBE (Dutch pronunciation: [ˈbɛrnɑrd ˈhaːi̯tɪŋk]) (born 4 March 1929) is a Dutch conductor and violinist.

Haitink was born in Amsterdam, the son of Willem Haitink and Anna Haitink. He studied music at the conservatoire in Amsterdam. He played the violin in orchestras before taking courses in conducting under Ferdinand Leitner in 1954 and 1955.

Haitink became second conductor of the Netherlands Radio Union Orchestra in 1955. He took the post of chief conductor of the Netherlands Radio Philharmonic in 1957. His conducting debut with the Concertgebouw Orchestra was on 7 November 1956, substituting for Carlo Maria Giulini. After the sudden death of Eduard van Beinum, Haitink was named first conductor of the Concertgebouw Orchestra on 1 September 1959. He became principal conductor of the Concertgebouw Orchestra in 1961, and shared that position jointly with Eugen Jochum until 1963, when Haitink became sole principal conductor. With the Concertgebouw Orchestra, Haitink made many recordings for the Philips label, and later Decca and EMI Classics, and toured widely with the orchestra.