A4
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## A4

A4 — Sets the base frequency for pitch A4.

## Description

These statements are global value assignments, made at the beginning of an orchestra, before any instrument block is defined. Their function is to set certain reserved symbol variables that are required for performance. Once set, these reserved symbols can be used in expressions anywhere in the orchestra.

## Syntax

    A4 = iarg

## Initialization

A4 = (optional) -- set reference frequency for pitch A4 to iarg Hertz. The default value is 440.

In addition, any global variable can be initialized by an init-time assignment anywhere before the first instr statement. All of the above assignments are run as instrument 0 (i-pass only) at the start of real performance.

Beginning with Csound version 6.08, A4 may be used. It affects the behaviour of the opcodes cpspch, cpsoct, cps2pch, cpsxpch and cpsmidinn.

## Examples

Here is an example of the A4 opcode. It uses the file A4.csd.

Example 34. Example of the A4 opcode.

See the sections Real-time Audio and Command Line Flags for more information on using command line flags.

    <CsoundSynthesizer>
    <CsOptions>
    ; Select audio/midi flags here according to platform
    -odac      ;;;realtime audio out
    ; For Non-realtime ouput leave only the line below:
    ; -o A4.wav -W ;;; for file output any platform

    ; By Stefano Cucchi - 2020

    </CsOptions>
    <CsInstruments>

    sr = 44100
    ksmps = 32
    nchnls = 2
    0dbfs = 1

    #define STANDARDPITCH #440# ; as set by ISO 1975:16 - STANDARD MUSICAL PITCH
    #define BAROQUEPITCH #415# ; common use (but not standard) in Baroque era (1600 - 1750)
    #define HIGHER #443# ; some orchestras, mainly in Europe use higher pitch (442-443 Hz)

    #define EXPRESSION #(440*1.3)+200# ; you can use an expression

    A4 = $STANDARDPITCH
    ;A4 = $BAROQUEPITCH
    ;A4 = $HIGHER

    ;A4 = $EXPRESSION

    instr 1

    ipch =	p4
    icps =	cpspch(ipch)
    asig	oscil 0.7, icps, 1
    	outs  asig, asig

    endin

    </CsInstruments>
    <CsScore>

    f 1 0 4096 10 1 0.3 0.2. 0.1

    ; Theme from Bach BWV 578 -  Little fugue in G minor.
    i 1 0 1 7.07
    i 1 + 1 8.02
    i 1 + 1.5 7.10
    i 1 + .5 7.09
    i 1 + .5 7.07
    i 1 + .5 7.10
    i 1 + .5 7.09
    i 1 + .5 7.07
    i 1 + .5 7.06
    i 1 + .5 7.09
    i 1 + 1 7.02
    e

    </CsScore>
    </CsoundSynthesizer>

## See also

Orchestra Header Statements

## Credits

Authors: John ffitch
September 2016

New in Csound Version 6.08

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