The Piano Duet -

Because players must sit side-by-side, their elbows, knees, and hands frequently brush against or even cross over each other.

This physical proximity was so striking that critics of the era sometimes referred to duet partners as "four-handed monsters," viewing the practice with a mix of fascination and moral suspicion. The Piano Duet

An interesting feature of the piano duet, specifically "piano four-hands" (two players on one instrument), is its secret history as a 19th-century "social lubricant" and the primary way people "listened" to music before the invention of the phonograph. The "Social Lubricant" of the 19th Century Because players must sit side-by-side, their elbows, knees,