Serialism is a rigorous system of composing music in which various elements of the piece are ordered according to a pre-determined ordered set or sets, and variations on them. The elements thus controlled may be the pitch of the notes, their length, their dynamics, their accents, or virtually any other musical quantity, which, in serial terms is called a parameter. More generally, serialism is any music which uses any ordered sets applied to any musical element.
Whilst researching serialism I came across a quote which I find very relevant to our studies at the moment. The quote reads: "Serial music is like spinach. People grow up hearing others complain about how terrible it is. Some people eventually try it and agree that it's horrible stuff; others try it and decide it's rather good. But most avoid and detest it as a result of rumour and hearsay." Although it is not necessary to enjoy serialism, one who is interested in classical music should attempt to understand it.
Twelve tone music which was established by Schoenberg is often referred to as serialism, but strictly speaking serialism is the sequel to Schoenberg's works, and came about in the late 1940's. Composers, led by Pierre Boulez and Karlheinz Stockhausen started to apply Schoenberg's 12-tone principle to more than just pitch. To recap, Schoenberg created tone rows, where the 12 different pitch classes of the scale are arranged in a particular order, then inverted, then played in reverse (retrograde) and then the retrograde inversion is played, and thus Schoenberg simply manipulated the pitch. For serialists, the basic pattern to be manipulated is determined not only by each note's pitch but by its rhythm, dynamics and timbre.
*Listen Boulez Structures pour deux pianos
When a tone row is turned backwards, its rhythmic pattern is also reversed. For example, a minum followed by a quaver followed by a semi-quaver becomes a semi-quaver followed by a quaver followed by a...