3. Repetition and Modulation

New objects: loadbang, float, %, select, mtof, counter?

Review previous patch

• control objects
  • metro, random, math (addition)
• audio objects
  • *~, line~ and the $1 in the message, vline~
• help menu
  • right-click and select help
  • ⌘E, select and copy useful bits into the patch

A simple sequencer from “off-the-shelf” parts

• Review lesson 2 patch
  • remember what metro does in the patch
    • fires bang to two objects, one to control the envelope
    • second sequence to randomly select a frequence
• copy lesson 2 patch to a new patch for the sequencer
  • keep the envelope parts
  • remove the freq parts
• how do we build a counter for a seqencer?
  • requirements:
    • step forward at regular intervals
    • loop back to the beginning when it reaches the end of a sequence
    • do something different at each step
  • Help > Browser > Pure Data > 2.control.examples > 05.counter
    • float
      • float holds a number from it’s right inlet, and sends out when it receives a bang to the hot inlet
      • Float objects are so common, they can be abbreviated to just f.
    • copy first example counter into working patch
    • use modulo (%) to create the loop
      • start with a small number
• use select to pick a different action for each step
  • note that we control the number of outlets on select
  • show with bangs
  • the extra outlet is for “none of the above”
  • use midi note names instead of frequency numbers (Google “MIDI note table” or just remember that 60 is middle C)
    • mtof will handle the conversion of midi to frequencies for osc~
  • send frequency values over to osc~ left (hot) inlet

What else could we do with the sequencer we built?

• change pitch
• change volume
• change tempo
• change envelope
• change timbre
• stop completely?

• use the same counter with a different % and a different select to create loops at different rates 🤯

• a note on counter
  • does a lot more than our counter
  • built in to a Pd external
  • install with the Cyclone external (already included in Purr Data)
    • Help > Find externals, search for Cyclone
    • select the one for your platform
    • now you can create counter objects

Amplitude Modulation

• osc~ is currently used in our patch to control the position of a speaker element
  • it outputs a range of -1 to 1, and we’re shaping that output with *~ at two stages
  • the last stage is the overall volume
  • the one before that is applying the envelope
• osc~ can also be used to change the inputs or outputs of another oscillator
• amplitude modulation occurs when we use one oscillator to control (modulate) the amplitude of another oscillator
• demo: add amplitude modulation
  • temporarily disconnect envelope (vline~)
  • make a new osc~ with a low number argument (2-5) and connect to the right inlet of *~
    • low modulation frequencies create a tremolo effect
  • we can affect the amount of the modulation by multiplying the output of the mod osc before we apply it to the carrier signal
  • note the fun ring effects of higher mod freqs
  • create sliders for mod freq and amounts
  • bring back the envelope controller
  • carrier sig => amplitude modulation => envelope => final volume => dac

Frequency Modulation

Homework: Watch Rafael Hernandez’s tutorial on FM Synthesis: https://youtu.be/DgeTHuDSgC0