A Gospel harmony is an attempt to merge or harmonize the canonical gospels of the Four Evangelists into a single gospel account. The earliest known example is the Diatesseron by Tatian in the 2nd century.

A harmony may be undertaken by scholars to establish a chronology for the events of the life of Jesus depicted in the four canonical gospels to better understand how the accounts relate to each other, identify features of a shared source document, or to establish events in the life of a Historical Jesus. Harmonies may also be undertaken to create narratives for artistic purposes, as in the creation of text for an oratorio or a script for a film.

The scholarly process is complicated by issues of text (such as the endings of Mark), discrepancies in details given about certain events (as in the empty tomb narratives), the place if any to be assigned non-canonical gospels of great antiquity such as the Gospel of Thomas, and issues of literary character (the pronounced differences between the Gospel of John and the Synoptics). Unique material in each Gospel resists distillation into a single harmonized chronology, as the variety of readings that appear in multiple harmony efforts attests. However, exploration of the unique material in Gospel accounts plays an important role in settling questions of authorship date, and an understanding of parallels helps to set these unique features in relief. The historical reliability of the Gospels continues to be a subject of debate.

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".