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<H2><A ID="SECTION007106000000000000000">
MIDI-style synthesizer</A>
</H2>
<P>
Example C10.monophonic.synth.pd (Figure <A HREF="#fig03.16">3.16</A>) also implements a monophonic,
note-oriented synthesizer, but in this case oriented toward MIDI
controllability. Here the tasks of envelope generation and sequencing pitches
are handled using control streams instead of audio signals. New
control objects are needed for this example:
<P>
<DIV ALIGN="CENTER"><A ID="fig03.16"></A><A ID="3787"></A>
<TABLE>
<CAPTION ALIGN="BOTTOM"><STRONG>Figure 3.16:</STRONG>
A MIDI-style monophonic synthesizer.</CAPTION>
<TR><TD><IMG
WIDTH="496" HEIGHT="459" BORDER="0"
SRC="img351.png"
ALT="\begin{figure}\psfig{file=figs/fig03.16.ps}\end{figure}"></TD></TR>
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<P>
<BR><!-- MATH
$\fbox{ $\mathrm{notein}$}$
-->
<IMG
WIDTH="62" HEIGHT="40" ALIGN="MIDDLE" BORDER="0"
SRC="img352.png"
ALT="\fbox{ $\mathrm{notein}$}">:
<A ID="3851"></A>MIDI note input. Three outlets give the pitch, velocity, and channel of
incoming MIDI note-on and note-off events (with note-off events appearing as
velocity-zero note-on events). The outputs appear in Pd's customary
right-to-left order.
<P>
<BR><!-- MATH
$\fbox{ $\mathrm{stripnote}$}$
-->
<IMG
WIDTH="81" HEIGHT="40" ALIGN="MIDDLE" BORDER="0"
SRC="img353.png"
ALT="\fbox{ $\mathrm{stripnote}$}">:
<A ID="3852"></A>filter out note-off messages. This passes
(pitch, velocity) pairs through whenever the velocity is nonzero, dropping
the others. Unlike <TT>notein</TT>, <TT>stripnote</TT> does not
directly use hardware MIDI input or output.
<P>
<BR><!-- MATH
$\fbox{ $\mathrm{trigger}$}$
-->
<IMG
WIDTH="65" HEIGHT="40" ALIGN="MIDDLE" BORDER="0"
SRC="img354.png"
ALT="\fbox{ $\mathrm{trigger}$}">,
<BR><!-- MATH
$\fbox{ $\mathrm{t}$}$
-->
<IMG
WIDTH="25" HEIGHT="39" ALIGN="MIDDLE" BORDER="0"
SRC="img355.png"
ALT="\fbox{ $\mathrm{t}$}">:
<A ID="3853"></A>copy a message to outlets in right to left order, with type conversion. The
creation arguments ("b" and "f" in this example) specify two outlets, one
giving "bang" messages, the other "float" (i.e., numbers). One outlet
is created for each creation argument. The outputs appear in Pd's standard
right-to-left order.
<P>
The patch's control objects feed frequencies to the <TT>phasor~</TT> object
whenever a MIDI note-on message is received. Controlling the amplitude (via
the <TT>line~</TT> object) is more difficult. When a note-on message is
received, the <TT>sel 0</TT> object outputs the velocity at right (because
the input failed to match 0); this is divided by the maximum MIDI velocity of
127 and packed into a message for <TT>line~</TT> with a time of 100 msec.
<P>
However, when a note-off is received, it is only appropriate to stop the sound
if the note-off pitch actually matches the pitch the instrument is playing.
For example, suppose the messages received are "60 127", "72 127",
"60 0", and "72 0". When the note-on at pitch 72 arrives the pitch should
change to 72, and then the "60 0" message should be ignored, with the note
playing until the "72 0" message.
<P>
To accomplish this, first we store the velocity in the upper <TT>float</TT> object. Second, when the pitch arrives, it too is stored (the lower
<TT>float</TT> object) and then the velocity is tested against zero (the
"bang" outlet of <TT>t b f</TT> recalls the velocity which is sent to
<TT>sel 0</TT>). If this is zero, the second step is to recall the pitch and
test it (the <TT>select</TT> object) against the most recently received
note-on pitch. Only if these are equal (so that "bang" appears at the
left-hand-side outlet of <TT>select</TT>) does the message "0 1000" go to the
<TT>line~</TT> object.
<P>
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<ADDRESS>
Miller Puckette
2006-12-30
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