A madrigal is a kind of song from the 1500s, especially in Italy and later in England. Several voices sing it together, usually with no piano, no guitar, no instruments at all. The parts weave around each other rather than all singing the same tune. The words are often about love or the countryside, not about church. Though actually, people sometimes stretch madrigal to mean any short, pretty love song, or a poem in that mood; the strict sense is this old song for several voices. You meet it in music class and in the history of music, not in everyday chat. It is not a carol, and it is not one person singing with a piano.