Music producers are using the mixing process to make songs sound louder. Songs are compressed into a narrow dynamic range at peak volume. On his blog Music Machinery, Paul Lamere's analysis shows that a song recorded recently is often less varied in volume than older recordings. Below, Katy Perry's "California Girls" (in red) compared with Led Zeppelin's "Stairway to Heaven" (in blue)"

Many drummers now record while listening to an electronic metronome or "click track." This steadies their playing and makes editing easier - snippets can be swapped without worrying about tempo deviations. But critics say click tracks make songs sound stiffer than those with slight tempo deviations. Lamere developed a way to analyze data to reveal the use of click tracks by drummers. Below, Green Day's "American Idiot" (in red) compared with The Beatles's "Dizzy Miss Lizzie" (in blue)"

This visualization by M.I.T musicologist Michael Cuthbert shows how Frederic Chopin used pitch in a series of mazurkas he wrote over the course of his life.