The Medieval era gave rise to the musical practice of polyphony, or having two or more vocal parts sung at once in a piece of music. The practice of polyphony was an evolution from plainsong, or Gregorian chant.
During Medieval times, the first organs were designed to be moved from place to place. It wasn't until the 1300s that larger, more permanent organs were built and used.
In the Renaissance period (1450 to 1600), there were three main types of music: sacred, secular and instrumental. All three of these types were characterized by group choirs, smooth rhythms, balanced phrases and harmonies utilizing triads.
The Romantic Period (1825 to 1900) saw the rise of program music. Program music told a story or carried with it a supposed deeper meaning. This practice is not unlike the rock concept albums of today, which often tell stories or convey a deeper message.
Twentieth century musical recordings changed the face of the music world, allowing people anywhere in the world to hear any kind of music. This technology ushered a worldwide combining of styles and genres.