Humorism, or humoralism, is a now discredited theory of the makeup and workings of the human body, adopted by Greek and Roman physicians and philosophers, positing that an excess or deficiency of any of four distinct bodily fluids in a person directly influences their temperament and health. From Hippocrates onward, the humoral theory was adopted by Greek, Roman and Islamic physicians, and became the most commonly held view of the human body among European physicians until the advent of modern medical research in the nineteenth century.

The four humors of Hippocratic medicine are black bile (Gk. melan chole), yellow bile (Gk. chole), phlegm (Gk. phlegma), and blood (L. sanguis), and each corresponds to one of the traditional four temperaments. A humor is also referred to as a cambium (pl. cambia or cambiums).

Essentially, this theory holds that the human body was filled with four basic substances, called humors, which are in balance when a person is healthy. All diseases and disabilities resulted from an excess or deficit of one of these four humors. These deficits could be caused by vapors that were inhaled or absorbed by the body. The four humors were black bile, yellow bile, phlegm, and blood. Greeks and Romans, and the later Muslim and Western European medical establishments that adopted and adapted classical medical philosophy, believed that each of these humors would wax and wane in the body, depending on diet and activity. When a patient was suffering from a surplus or imbalance of one fluid, then his or her personality and physical health would be affected. This theory was closely related to the theory of the four elements: earth, fire, water and air; earth predominantly present in the black bile, fire in the yellow bile, water in the phlegm, and all four elements present in the blood.

Paul Joseph Brady (born 19 May 1947) is an Irish singer-songwriter, whose work straddles folk and pop. He was interested in a wide variety of music from an early age. During his career he has passed through several major bands and on to a successful solo phase. Initially popular for playing traditional Irish music in a duo with Andy Irvine and later with Tommy Peoples and Matt Molloy, he later turned to a more rock inspired electric style with poignant political lyrics. Among his most popular songs are "Crazy Dreams", "Nothing but the Same Old Story", "The Island", "Night Hunting" (covered by Santana), and "Steel Claw" and "Paradise is Here"(covered by Tina Turner).

Arty McGlynn is an Irish guitarist born in Omagh, County Tyrone. In addition to his solo work, he has collaborated with different notable groups such as Patrick Street, Planxty, Four Men and a Dog, De Dannan and the Van Morrison Band. He played guitar on the critically acclaimed 1989 Van Morrison album, Avalon Sunset. He has also played duo performances and recordings with uilleann piper Liam O'Flynn his wife fiddle player Nollaig Casey.

Cillian Vallely is an Irish musician, born in Armagh, Northern Ireland. He plays traditional Irish music on the uilleann pipes and low whistle, and studied at the Armagh Pipers Club with his mother and father, Brian and Eithne, and then with the late Armagh piper Mark Donnelly. His brothers, Niall and Caoimhín, also play traditional music.

Since 1999, he has been a member of the band Lúnasa, with whom he has recorded 6 albums. He has also performed and toured with Riverdance, Natalie Merchant, Tim O Brien & Mary Chapin-Carpenter in The Crossing, New York-based Whirligig, and the Celtic Jazz Collective with Lewis Nash and Peter Washington. In the past couple of years, he has worked on various collaborations between traditional and classical music, along with his brother Niall and the composer Micheal O’Suilleabhain

He has recorded on over 40 albums including Callan Bridge with his brother Niall, On Common Ground with Kevin Crawford and various guest spots with Natalie Merchant, Alan Simon’s Excalibur project with Fairport Convention and Moody Blues, GAIA with the Prague Philharmonic Orchestra, and singer Karan Casey. He has recently recorded on two movie soundtracks, Irish Jam and The Golden Boys and played uilleann pipes on the BBC’s Flight of the Earls soundtrack.

Tony MacMahon ( Ennis, Co. Clare, Ireland, 1939) is an Irish button accordion player and broadcaster. Among his influences were accordionists Joe Cooley and Sonny Brogan, as well as piper Willie Clancy, fiddler Bobby Casey, and singer and piper Seamus Ennis.

He moved to Dublin in 1957, where he took accordion lessons from Sonny Brogan. Mick Mulcahy has cited him as an influence.

MacMahon, considered by some a purist or a traditionalist, was vocal in his criticism of the River of Sound program, initially on the Late Late Show, and subsequently in his address to the Crossroads Conference. He became embroiled in controversy again in August 2009 after calling the musician Alec Finn a "second rate accompanist," and claiming that neither he or Johnny 'Ringo' MacDonagh were musicians.