programming with max/msp - Virtual Sound

Interlude A - Programming with Max/MSP IA
Fig. IA.7 Summing numbers that contain decimal points
Everything that we have covered to this point about addition also applies to
subtraction, multiplication, and division. Try building the patch shown in Figure
IA.8 to verify that this is the case:
Fig. IA.8 Other mathematical operators
A brief piece of advice is in order at this point: do these exercises! Although
they may seem trivial, doing them will help you to notice the details and the
quirks of the Max/MSP environment, details whose importance will be revealed
in the patches that we will pursue in the following chapters. For example, in
the test case with the comment “floating point division and the use of the
message box”, you see that we are submitting a list of integers (“10 4”) for
evaluation. Despite the fact that integers are submitted, the operator was
already declared to represent a floating point operation, thanks to the floating
point argument provided in its object box, and as a consequence, the result
emitted will be a floating point number.
Let’s again use some of these simple operations in a musical context. You’ll
remember how the distance between two notes, an interval, can be expressed
as a ratio between the two frequencies. For example, the interval of a fifth,
corresponding to 7 semitones, can be expressed using the ratio 3/2. Given a
frequency (let’s say 261.63 Hz, which is middle C), if we multiply the frequency
by 3 and then divide by 2, we will obtain the frequency for the note a fifth
above (which in this case would turn out to be 392.44 Hz, a G). To see this in
action, open the file IA_02_fifth.maxpat (shown in Figure IA.9):
In the patch we see that the note number generated by the kslider is
transformed into frequency though the use of mtof, and is then sent to a
saw~ oscillator. The output of mtof is also multiplied by 3/2, in order to obtain
the frequency needed to sound the note a fifth above, which is then sent to a
second saw~ oscillator. Note that the arguments to the multiplier object and
from “Electronic Music and Sound Design” Vol. 1 by Alessandro Cipriani and Maurizio Giri
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