Algorithmic Composition: A Gentle Introduction to Music Composition Using Common LISP and Common Music

Glossary

1/f noise - a class of noise whose values correlate logarithmically with past values.

Absolute Referencing - referencing a container by name.

Algorithm - a rule or procedure used to solve a problem.

Algorithmic Composition - the use of computers to implement procedures that result in the generation of music.

Applicative programming - a technique that allows a function to be applied to each element of a list.

Array - a data type that stores information in indexed locations. Arrays may store data in multiple dimensions.

Atom - any LISP object that is not a cons cell. NIL is both an atom and a list.

Brownian motion or 1/f ² noise - Brownian motion is the observed movement of small particles randomly bombarded by the molecules of the surrounding medium. Brownian motion is also referred to as 1/f ² noise.

Cardinality - the number of elements in a set.

Class - a data type that supports inheritance for slots, slot defaults, and methods.

Color - the pitch sequence of an isorhythmic motet.

Common LISP Object System (CLOS) - a set of tools used to develop object-oriented programs in LISP.

Conditionals - a category of Common LISP forms that choose an action based on an evaluation.

Cons Cell - a portion of computer memory comprised of two parts: the CAR and the CDR. Lists are made up of cons cells.

Data - information.

Data Type - a classification of data. LISP supports many data types including integers, floating point values, ratios, symbols, strings, and lists.

Dotted List - a cons cell whose CDR points to a non-NIL atom.

Element - an object in a set.

Empty List - a list with no elements or the empty list. May be represented as () or NIL.

Encapsulation - the act of placing one thing inside of another.

Flat List - a list that does not contain any lists as elements.

Floating Point Number - a number that contains a decimal point.

Frozen Generator - a generator whose elements have been computed once and will remain fixed until the generator is unfrozen and re-computed.

Function - an operation that performs a procedure and returns a result.

Global variable - a variable that exists in the global lexical context.

Information clause - a phrase used in conjunction with the Common Music map command to get information about an object or objects.

Inheritance Link - a connection between classes that enables information about slots and methods to flow hierarchically from description of classes to description of individuals.

Integer - a whole number.

Isorhythm - literally means "same rhythm." The compositional practice of mapping a rhythmic pattern onto a pitch sequence.

Item stream - an ordering of objects based on pattern types.

Item stream accessor - retrieves one value at a time from the item stream.

Item stream data types - the kinds of information that may be assigned to slots. Item stream data types end in the letter "s." For example, amplitudes, notes, and rhythms are item stream data types.

Item stream macros - a function used in conjunction with item streams to elicit a particular behavior. Examples of Item Stream Macros include chord, crescendo, and diminuendo.

Item stream pattern type - the ordering of objects in an item stream. Examples of item stream pattern types include cycle, heap, palindrome, and random.

Iteration - a repeating process.

Keyword argument - a symbol that begins with a colon that modifies the behavior of a procedure.

Lambda expressions - unnamed or anonymous functions.

Lexical closure - a procedure that creates an environment in which a variable is known.

Lexical context - the region in which a variable is may be referenced.

LISP - a programming language that derives its name from List Processing.

List - a data type that is represented as a chain of cons cells.

Local variable - a variable that exists in a local lexical context such as a LET or LET*.

Macro - a function designed to serve as a group of functions.

Mapping - the process of transforming a range of values onto another range of values.

Markov Process - a probability system where the likelihood that an event will be selected is based on one or more past events. A matrix referred to as a transition table is used to show the probability that a certain event will be selected based on one or more past events. The order of the transition table is dependent on the number of past events considered in the selection of the next event. A first-order transition table describes the probability that an event will be selected given one past event and a second-order transition table describes the probability that an event will be selected given two past events. The succession from one event to the other is called a markov chain.

Member - an object in a set.

Nested List - a list that contains one or more lists as an element.

Object - an instance of a data type.

Octatonic Scale - a series of eight pitches that alternate whole and half steps for one octave.

Palindrome - a pattern that reads the same forwards as it does backwards.

Pitch Class - an integer in the range 0-11 that represents a symbolic note name.

Pitch Class Set (pc set) - a collection of integers representing pitch classes.

Pointer - a pointer gives the address to an object in memory.

Predicate - a function that returns a T or NIL evaluation.

Prime Form - the arrangement of pitch classes such that the smallest intervals are at the beginning of the set, the interval between the first and last members of the set is smaller than the interval between the last and first members of the set, and the first pitch class is 0.

Primitive - a Common LISP built-in function.

Probability - the study of outcomes that produce a given event to the total number of possible outcomes. A probability is the likelihood that a particular event will occur. A probability is expressed as a ratio- the likelihood that a given event will occur in relation to the total number of possible outcomes.

Ratio - a fractional number made up of a numerator and a denominator.

Recursion - something that is defined in terms of itself.

Recursive function - a function that calls itself.

Relative Referencing - referencing a container by its position in the object hierarchy.

Scope - the region of a program in which an object may be referenced.

Serial Composition - a method of composition where tonality is undermined by applying a series to the organization of musical parameters such as pitch and rhythm.

Set - a collection of objects

Slot - a place to store values for a class.

Stella -Common Music's command interpreter.

Stochastic Music - the use of probability theory in the selection of musical parameters.

String - a succession of characters enclosed in double quotes.

Subclass - an object one-level below in a class hierarchy.

Superclass - an object one-level above in a class hierarchy.

Symbol - a LISP data type.

Talea - the rhythmic pattern of an isorhythmic motet.

Tone Row - a sequence of 12 chromatic pitches where no pitch is repeated.

Truth Table - a table representation that shows a T or NIL evaluation when two or more expressions are combined by a logical operator.

User-Defined Function - a function defined by the user, e.g. not a primitive.

Variable - a place in memory where data is stored. Common LISP and Common Music variables are named by symbols.

Well-Formed List - a list that has an equal number of left and right parentheses.

White noise or 1/f ⁰ noise - a class of noise that results when all events have an equal probability of being selected. White noise has a flat spectrum meaning that its energy is dispersed evenly throughout a specified range. White noise is also referred to as 1/f ⁰ noise because of its flat spectrum.