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<TITLE>GLOBAL_STEREO_REVERB</TITLE>
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<H2>Toot 9: Global Stereo Reverb</H2>
<P>In the previous example you may have noticed the soundin source being
"cut off" at ends of notes, because the reverb was <B>inside
</B>the instrument itself. It is better to create a companion instrument,
a global reverb instrument, to which the source signal can be sent. Let's
also make this stereo.</P>
<P>Variables are named cells which store numbers. In Csound, they can be
either <I>local</I> or <I>global</I>, are available continuously, and can
be updated at one of four rates - setup, <B>i</B>-rate, <B>k</B>-rate,
or <B>a</B>-rate. </P>
<P><B><A HREF="./../Syntax/const.html">Local Variables</A></B>
(which begin with the letters <B>p</B>, <B>i</B>, <B>k</B>, or <B>a</B>)
are private to a particular instrument. They cannot be read from, or written
to, by any other instrument. </P>
<P><B><A HREF="./../Syntax/const.html">Global Variables</A></B>
are cells which are accessible by all instruments. Three of the same four
variable types are supported (<B>i</B>, <B>k</B>, and <B>a)</B>, but these
letters are preceded by the letter <B>g</B> to identify them as "global."
Global variables are used for "broadcasting" general values,
for communicating between instruments, and for sending sound from one instrument
to another.</P>
<P>The reverb instr99 below receives input from instr9 via the global a-rate
variable garvbsig. Since instr9 <I>adds into</I> this global, several copies
of instr9 can do this without losing any data. The addition requires <I>garvbsig</I>
to be cleared before each k-rate pass through any active instruments. This
is accomplished first with an <B><A HREF="./../Syntax/assign.html">init</A></B>
statement in the orchestra header, giving the reverb instrument a higher
number than any other (instruments are performed in numerical order), and
then clearing <I>garvbsig</I> within instr99 once its data has been placed
into the reverb.</P>
<PRE><TT> sr = 18900 ; toot9.orc
kr = 945
ksmps = 20
nchnls = 2 ; stereo
garvbsig init 0 ; make zero at orch init time
instr 9
idur = p3
iamp = p4
iskiptime = p5
iattack = p6
irelease = p7
ibalance = p8 ; panning: 1=left, .5=center, 0=right
irvbgain = p9
kamp linen iamp, iattack, idur, irelease
asig soundin "soundin.aiff", iskiptime
arampsig = kamp * asig
outs arampsig * ibalance, arampsig * (1 - ibalance)
garvbsig = garvbsig + arampsig * irvbgain
endin
instr 99 ; global reverb
irvbtime = p4
asig reverb garvbsig, irvbtime ; put global signal into reverb
outs asig, asig
garvbsig = 0 ; then clear it
endin </TT>
</PRE>
<P>In the score we turn the global reverb on at time 0 and keep it on until
irvbtime after the last note.</P>
<PRE><TT>; ins strt dur rvbtime ; toot9.sco
i99 0 9.85 2.6
; ins strt dur amp skip atk rel balance(0-1) rvbsend
i9 0 1 .5 0 .02 .1 1 .2
i9 2 2 .5 0 .03 .1 0 .3
i9 3.5 2.25 .5 0 .9 .1 .5 .1
i9 4.5 2.25 .5 0 1.2 .1 0 .2
i9 5 2.25 .5 0 .2 .1 1 .3
e</TT>
</PRE>
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