Medieval music is the vocal and instrumental music written and performed during The Middle Ages in Europe, from the 6th to 15th centuries. That would mean all music written in notation and song lyrics preserved in the period before The Renaissance began. Because the modes of writing music were just being invented in this period, sources are scarce before the ninth century. Before that, we have some treatises, some debates on how music should be performed, and paintings of people singing and playing, but little notation of what people actually played and sang.
The term "medieval music" is wide in itself, because it spans a lot of genres and national styles, and several hundred years. Thus, a long list of sub-genres may be produced. Because most of the theoretical attention was given to church music, it is a natural place to begin. From there, we may proceed to secular (non-church) music and national styles, and the difficult topic of musical theory. Usually, medieval church music is reckoned to be the starting point of western Classical Music, because of the emergence of musical notation.
Church Music
The Trope Maker for the Ominous Latin Chanting. It began with monks chanting the mass, and melodies corresponding to the different parts of mass, all in Latin, of course. But the Gregorian tradition had to take shape first, and behind this were a number of local styles. Thus, the Christian principalities in Spain used the Bessarabian style, based on the Gothic mass performance from before the Moor conquest. The French had their Galician style, based on early clerical traditions before the Franks took hold in the area. The Italians had their own Romanesque singing, based on the performance in Milan and coined by St. Ambrose, and the British Isles had several unique ones, with an honorable mentioning of the Celtic church in Ireland.
The Pope wished for some sort of clerical unity. This unity was provided by the Franks when Charles the Great, or Charlemagne made a number of conquests, molded Europe more into one state for the time being, and put the Pope squarely on his side. His cultural transition is named the Carolingian Renaissance because of a sincere wish to make the old Roman ways standard again. In this time, the standard repertoire of music was born, and every church had to comply with it. The older styles were discarded.
At the same time, notation arose, but the earliest experiments were not like anything we know of today. It was called daseian, and was borrowed from the Byzantine court. It was later replaced with the neume system.
Some of this music was holy, and the holiest music was the melodies connected to the fixed parts of mass. They were not to be used or tampered with. Second came the hymns, some of which were centuries old already. Third on the list was the "sequences", developed during this period and later.
After AD 1000, this development prospered when the singers developed a habit of singing at the end of the phrase by adding new melody notes (like singing more embellished notes on the last syllable of a Hallelujah). This new part of the singing was called a trope (This is actually the original "troping", by the way). From the tropes sprang the sequence, and thus a new genre of church music was born. Inside the church, music became more and more diverse. One of the first "tropers" was Notker Balbulus, a monk who put new words to the trope and made a sequence out of it.
Secular (non-religious) Music
The troubadours and trouvères sang about their undying, noble love for a beautiful lady. They probably strummed lutes (a guitar-like instrument) to accompany themselves and they may have had what was in effect a "backup band" of instrumentalists. They were usually as good at crafting poetry as they were at singing and playing.
The troubadours sung in Occitan (nowadays the language of Catalan) and the trouvères sung in Old French. They wandered around as traveling bards, entertaining at aristocratic manors and castles. They sang about bravery in battle, being chivalrous and noble, but most of all, they sang about Courtly Love. When a troubadour or trouvere was at an inn and they got a huge crush on the barmaid, that's an everyday attraction. Courtly Love is when the singer has fallen in love with a distant (or even unobtainable) princess, who they woo from afar. The singer then professes his love for her in a polite, respectful, and poetic fashion.
See also Medieval Ballads.
Polyphony
Polyphony which is independent interweaving melodies, developed gradually, and this is also connected to the troping. From the beginning, people sang in octaves, then in fifths. When we reach the 12th century, improvisation became common, and over the next century the first polyphonic (two or more independent melodies at once) style arose: Ars Antiqua or the "Notre Dame School", because the composers, whose names are remembered today, were clerics at the Notre Dame cathedral in Paris. Priests who also wrote music were a staple in this era, and continued to be for another century and a half. The style is also called Organum because the original holy mass melody was sung very slowly over one, two or three different, probably improvised voices.Much of this was written down, because over the centuries, musicians invented a notational system of four lines, enough for the singers to interpret music from, or for composer to write melodies.
A note on theory: The neumatic system was developed in the eleventh century, and also a new way of singing, courtesy of the reformer Guido of Arezzo. From this point, two traditions arose, who never came to terms on how to sing. But Guido had papal support, and the other fraction grudgingly accepted. From the Guidonic tradition, we have the ut, re, mi, fa sol (commonly known as C, D, E, F, G) tradition, from the others, the monochord fraction, we have the note names: A, B, C, D, E, G.
Ars Nova
By the turn of the fourteenth century, Western music already had a polyphonic tradition and a music theory, but by this time, some Italian and French spoilsports had to break this system apart. A traditional period, Ars Nova, emerged, creating the need for new notation and a vastly more experimental music. It also laid the groundwork for a secular written tradition, taking it to new artistic levels. When this style died out, The Renaissance was already on its way.
The line between the end of the medieval era and the start of the Renaissance era is blurry. The 15th century music is transitional, since it mixes Middle Ages approaches (polyphonic music with highly differentiated lines), and Renaissance styles (for example the new Franco-Flemish sound and more equal polyphonic parts). The sweet-sounding interval of the third was more prominent, which is a mark of the shift to the Renaissance musical style.
