The earliest Madrigal was a monophonic form of vocal music during the 14th century Medieval Italy. Originally, the style referred to the popular Italian songs of this time. With the discovery of polyphonic writing, music began to carry separate voices. These early madrigals were basically acapella and usually worded to existing poetry. They were also easy enough for even amateur singers. Usually four to six vocalists or as many as ten would sing unaccompanied by any instruments.
The madrigal's origins are unclear; however it is speculated to have come from the Latin word 'matricale' meaning “in the mother tongue”; i.e., Italian, not Latin. In the 14th century, the madrigal was a poetic form of a few stanzas. Each verse was set to the same music with the final verse concluding the idea behind the song. The music of the time now had numerous parts but still sang the same melody. Alas, composers sought harmony. Counterpoint was yet to be discovered.
Many early madrigals used the 14th century love poetry of Francesco Petrarca (Petrarch) and were extremely popular. Then, the form seemed to fade with the 15th century. Many madrigals were indeed composed during this time but likely became somewhat overshadowed by the other newer forms of the Renaissance and the discovery of harmony. Composers like Orlando Lassus, Adriaan Willaert, and Claudio Monteverdi played very influential roles in the madrigal movement.
In the latter 16th century, about 1580s or so, the madrigal made its way to England where it found a eager audience. English composers too picked up the style and created some of the most renowned madrigals to date. English composers William Byrd, Thomas Morley, and John Wilbye were fond of the madrigal style just to name a few. Morley compiled and published an anthology of madrigals by some twenty composers entitled "The Triumphes of Oriana," a tribute to Elizabeth the First.
Mid Renaissance Madrigal
'Lo Son Ferito' (I Am Wounded)
Composed by Giovanni Pierluigi da Palestrina 1561
Early Baroque Madrigal
'Oft Have I Vowed'
Composed by John Wilbye 1609