// Csound single-line comments can be preceded by a pair of forward slashes... ; ...or a semicolon. /* Block comments begin with /* and end with */ // Orchestras begin with a header of audio parameters. nchnls = 1 nchnls_i = 1 sr = 44100 0dbfs = 1 ksmps = 10 // The control rate kr = sr / ksmps can be omitted when the number of audio // samples in a control period (ksmps) is set, but kr may appear in older // orchestras. kr = 4410 // Orchestras contain instruments. These begin with the keyword instr followed // by a comma-separated list of numbers or names of the instrument. Instruments // end at the endin keyword and cannot be nested. instr 1, N_a_M_e_, +Name // Instruments contain statements. Here is a typical statement: aSignal oscil 0dbfs, 440, 1 // Statements are terminated with a newline (possibly preceded by a comment). // To write a statement on several lines, precede the newline with a // backslash. prints \ "hello, world\n";comment // Csound 6 introduced function syntax for opcodes with one or zero outputs. // The oscil statement above is the same as aSignal = oscil(0dbfs, 440, 1) // Instruments can contain control structures. kNote = p3 if (kNote == 0) then kFrequency = 220 elseif kNote == 1 then // Parentheses around binary expressions are optional. kFrequency = 440 endif // Csound 6 introduced looping structures. iIndex = 0 while iIndex < 5 do print iIndex iIndex += 1 od iIndex = 0 until iIndex >= 5 do print iIndex iIndex += 1 enduntil // Both kinds of loops can be terminated by either od or enduntil. // Single-line strings are enclosed in double-quotes. prints "string\\\r\n\t\"" // Multi-line strings are enclosed in pairs of curly braces. prints {{ hello, world }} // Instruments often end with a statement containing an output opcode. outc aSignal endin // Orchestras can also contain user-defined opcodes (UDOs). Here is an // oscillator with one audio-rate output and two control-rate inputs: opcode anOscillator, a, kk kAmplitude, kFrequency xin aSignal vco2 kAmplitude, kFrequency xout aSignal endop instr TestOscillator outc(anOscillator(0dbfs, 110)) endin // Python can be executed in Csound // . So can Lua // . pyruni {{ import random pool = [(1 + i / 10.0) ** 1.2 for i in range(100)] def get_number_from_pool(n, p): if random.random() < p: i = int(random.random() * len(pool)) pool[i] = n; return random.choice(pool) }} // The Csound preprocessor supports conditional compilation and including files. #ifdef DEBUG #undef DEBUG #include "filename.orc" #endif // The preprocessor also supports object- and function-like macros. This is an // object-like macro that defines a number: #define A_HZ #440# // This is a function-like macro: #define OSCIL_MACRO(VOLUME'FREQUENCY'TABLE) #oscil $VOLUME, $FREQUENCY, $TABLE# // Bodies of macros are enclosed in # and can contain newlines. The arguments of // function-like macros are separated by single-quotes. Uses of macros are // prefixed with a dollar sign. instr TestMacro aSignal $OSCIL_MACRO(1'$A_HZ'1) // Not unlike PHP, macros expand in double-quoted strings. prints "The frequency of the oscillator is $A_HZ Hz.\n" out aSignal endin // Here are other things to note about Csound. // There are two bitwise NOT operators, ~ and ¬ (U+00AC). The latter is common // on keyboards in the United Kingdom // . instr TestBitwiseNOT print ~42 print ¬42 endin // Csound uses # for bitwise XOR, which the Csound manual calls bitwise // non-equivalence . instr TestBitwiseXOR print 0 # 0 print 0 # 1 print 1 # 0 print 1 # 1 endin // Loops and if-then statements are relatively recent additions to Csound. There // are many flow-control opcodes that involve goto and labels. instr TestGoto // This... if p3 > 0 goto if_label goto else_label if_label: prints "if branch\n" goto endif_label else_label: prints "else branch\n" endif_label: // ...is the same as this. if p3 > 0 then prints "if branch\n" else prints "else branch\n" endif // This... iIndex = 0 loop_label: print iIndex iIndex += 1 if iIndex < 10 goto loop_label // ...is the same as this... iIndex = 0 loop_lt_label: print iIndex loop_lt iIndex, 1, 10, loop_lt_label // ...and this. iIndex = 0 while iIndex < 10 do print iIndex iIndex += 1 od endin // The prints and printks opcodes // , arguably // the primary methods of logging output, treat certain sequences of characters // different from printf in C. instr TestPrints // ^ prints an ESCAPE character (U+001B), not a CIRCUMFLEX ACCENT character // (U+005E). ^^ prints a CIRCUMFLEX ACCENT. prints "^^\n" // ~ prints an ESCAPE character (U+001B) followed by a [, not a TILDE // character (U+007E). ~~ prints a TILDE. prints "~~\n" // \A, \B, \N, \R, and \T correspond to the escaped lowercase characters (that // is, BELL (U+0007), BACKSPACE (U+0008), new line (U+000A), CARRIAGE RETURN // (U+000D), and tab (U+0009)). prints "\T\R\N" // %n, %r, and %t are the same as \n, \r, and \t, as are %N, %R, and %T. prints "%t%r%n" // %! prints a semicolon. This is a hold-over from old versions of Csound that // allowed comments to begin in strings. prints "; %!\n" endin // The arguments of function-like macros can be separated by # instead of '. // These two lines define the same macro. #define OSCIL_MACRO(VOLUME'FREQUENCY'TABLE) #oscil $VOLUME, $FREQUENCY, $TABLE# #define OSCIL_MACRO(VOLUME#FREQUENCY#TABLE) #oscil $VOLUME, $FREQUENCY, $TABLE# // Uses of macros can optionally be suffixed with a period. instr TestMacroPeriodSuffix aSignal $OSCIL_MACRO.(1'$A_HZ'1) prints "The frequency of the oscillator is $A_HZ.Hz.\n" out aSignal endin // Csound has @ and @@ operator-like macros that, when followed by a literal // non-negative integer, expand to the next power of 2 and the next power of 2 // plus 1: // @x = 2^(ceil(log2(x + 1))), x >= 0 // @@0 = 2 // @@x = 2^(ceil(log2(x))) + 1, x > 0 instr TestAt prints "%d %2d %2d\n", 0, @0, @@0 prints "%d %2d %2d\n", 1, @1, @@1 prints "%d %2d %2d\n", 2, @2, @@2 prints "%d %2d %2d\n", 3, @3, @@3 prints "%d %2d %2d\n", 4, @4, @@4 prints "%d %2d %2d\n", 5, @5, @@5 prints "%d %2d %2d\n", 6, @6, @@6 prints "%d %2d %2d\n", 7, @7, @@7 prints "%d %2d %2d\n", 8, @8, @@8 prints "%d %2d %2d\n", 9, @9, @@9 endin // Including newlines in macros can lead to confusing code. instr MacroAbuse if 1 == 1 then prints "on\n" #define FOO# BAR #endif // This ends the if block. It is not a preprocessor directive. endin f 1 0 16384 10 1 i "N_a_M_e_" 0 2 i "TestOscillator" 2 2 i "TestBitwiseNOT" 0 1 i "TestBitwiseXOR" 0 1 i "TestGoto" 0 1 i "TestMacroPeriodSuffix" 4 1 i "TestAt" 0 1 i "MacroAbuse" 0 1 e