BEAP Analog Model Curriculum Outline
From Cycling '74 Wiki
Revision as of 01:42, 25 July 2013 by Ddg@cycling74.com
- What is the Analog Model?
- Based on modular synthesis techniques.
- Focuses on subtractive synthesis.
- Built off of four primary tools:
- Level Controls
- Why is this Important?
- It is the basis for most modular synth techniques.
- It is also the basis for a lot of synth-based music.
- It provides a useful way to do sound design iteratively.
- It sounds good, too!
- What is necessary for this workshop?
- A laptop with audio capability.
- A pair of headphones.
Oscillators and Tone Generation
- Oscillators are the way that synths make sound. They create repeated waveshapes at a set frequency.
- Select an Oscillator from the contextual menu (ctrl/right-click, then Paste From | BEAP | Oscillators | Oscillator).
- An oscillator by itself creates waveforms, but is not routed to our computer's output. For this, we need an Output Module.
- Select a stereo output from the contextual menu: Paste From | BEAP | Output | Stereo
- Connect the output of the oscillator to both inputs of the Stereo module.
- Turn on the DSP (this might need explaining), and you should hear a tone.
- The two most important setting of the oscillator are the tuning and the waveshape.
- Change the tuning by adjusting the offset knob on the front of the Oscillator module.
- Change the waveform by selecting a waveform image in the button matrix.
- Note how the waveform changes the timbre, but not the pitch, of the oscillator.
- More than one oscillator can be used at a time to create more interesting tonality.
- Select another Oscillator from the menu, or copy the existing one by option/alt-dragging the one already on-screen.
- Select the patchcord going to the right inlet of the Stereo module, then grab the top handle and drag it from the first to the second oscillator.
- Now you will hear an oscillator in each ear of your headphones. Adjust the offset and waveform in each to verify the changes.
- In order to have the two oscillators "mix" together, we need to use another device to combine them.
- Add an audio mixer using the Paste From | BEAP | Mixers | Audio option from the contextual menu.
- Connect the two oscillators to inputs 1 and 2 of the mixer, then connect the output of the mixer to the two Stereo inputs.
- Turn up the volume of the mixer channels to hear a mix of the tones. You can alter the volume of each oscillator to create a nicely blended tone.
- At this point, we are able to hear the oscillators, but it would be nice to change the pitch in a musical way.
- We need a controller, and will create a virtual keyboard using Paste From | BEAP | Input | Keyboard
- Connect the CV output to the 1V/Oct inputs of the oscillators. The terminology used here is from the modular synthesis world...
- Lock the patch and click on the keyboard keys. You should hear the pitch change to match the keyboard notes.
Level Control/Gating with a VCA
- One of the issues with our current system is that the oscillator tones never turn off.
- This is how analog oscillators work - they are never really "off", they are only muted.
- We can have our keyboard mute the signal if we use another module, and the gate output of the keyboard.
- The VCA - Voltage Controlled Amplifier
- The purpose of a VCA is to use incoming signal values to adjust the amplitude of a signal. In this case, we will use it to control the volume of the mixer output.
- Instantiate a VCA, then connect it between the Mixer and the Stereo Output module. The signal will immediately turn off.
- In order to turn a VCA "on", we need to send it a HIGH value whenever a key is pressed, then a LOW value when the key is released.
- This is done using the Gate output of the keyboard, which produces exactly those values as we play the keyboard.
- Connect the Gate output of the keyboard to the Control input of the VCA, then play the keyboard - and you will now hear the sound as expected.
- Saving Your Work
- At this point, we've put in enough work on our patch to want to save it. Those of you that have worked with Vizzie might be concerned that you will lose all of your work. But, in fact, all of the state is saved with our patch - part of the brilliance of BEAP.
- Select Save from the File menu and save the patch. Now, close the patch and Max, restart Max and select our saved patch from the "Recent Patches" menu. There we are - back where we started!
Filtering with an LPF
- One of the things that make synthesis more compelling is the manipulation of the raw sounds that the oscillator creates. We use a filter to do this - it can be used to change the harmonic content of the core sound, giving us a broader palette of sonic variety.
- The filter we are going to use is a Low Pass Filter (generally abbreviated as LPF), which dampens high frequencies while allowing low frequencies to pass through unchanged (hence its name).
- Select the LPF module from the Filters sub-menu and add it to your patch. Put it between the mixer and the VCA so that we can affect the entire sound.
- There are a few important control on this module. The cutoff frequency is the "fence" of the filter: everything above that frequency gets attenuated, while everything below that frequency is left unchanged.
- There is a Q control which is also important - it determines the characteristics of the filter right at the cutoff frequency. A high Q setting will accentuate the sound right at the cutoff point, giving the filter a bit of a "kick" right at that frequency. This makes things a little more biting, and makes the filter a more significant part of the overall tone.
- Try different settings while playing the keyboard. You should hear drastic changes in the sound of your created synth.
- A very high Q setting will "whistle", because you are creating a feedback circuit in the filter module.
- You can completely eliminate the sound with a low enough filter cutoff setting. This is because all of the frequencies created by the oscillators are fully attenuated by the filter. Some synthesizers use filtering, rather than a VCA, to control volume.
Modulating with Envelopes and LFO's
- At this point, we've got a working synthesizer complete with filtering. But it sound a little "blah". We need to spice it up, and "modulators" are the key.
- Modulators are the name given to modules that control the parameters of other modules.
- In some cases, you can thing of them as "Automators", since they automate the parameter changes based on some other process.
- In this section, we are going to look at two different modulators: The Envelope and The LFO (or Low Frequency Oscillator).
- Let's start with a simple envelope - the ASR Envelope.
- The characteristics of an ASR envelope is that it uses a gate signal - like we get from the keyboard device - and turns it into a contoured control signal.
- The acronym ASR stands for "Attack, Sustain, Release", and describes the three segments of this envelope: the attack "ramp-up" time, the sustain period (which remains until the note is released) and the release "ramp-down" time.
- Using an ASR envelope allows us to smooth the edges of the gate signal, giving us more musical control of the sound of the synth we are building.
- Now let's use the ASR envelope to make a smoother-sounding level change in our patch.
- Add an ASR module (found in the Envelope menu) to your patch, then connect the gate output of the keyboard to the gate input of the ASR.
- Next, connect the ASR CV output to the control input of the VCA (deleting the patchcord connecting it to the gate output of the keyboard.
- Now, play the keyboard, but change the attack and release times of the ASR. You will hear that a longer attack time gives us a smooth ramp-up into the sound, and a longer release time gives us a smoother release of the note. This makes the sound of the synth much more usable for ambient or pad-like sounds.
- Envelopes are cool with filters, too, but we are going to try something different - using an LFO (Low Frequency Oscillator) to change the filter sound.
- Add an LFO module to your patch, then connect the CV output to the filter's CV inputs.
- An LFO is an oscillator - similar to our sound generating device - but it runs at sub-audio rate. This means it can be used for gentle changes to other modules in a cyclical way.
- The LFO, like the Oscillator used earlier, runs forever - and at full output level. In order to "tame" the amount of modulation, we can use the modulation attenuators on the filter to reduce the amount of effect the LFO has on the filter cutoff.
- Creating a good LFO sound requires some fiddling with the baseline cutoff frequency, the modulation amount, and the LFO waveshape. Experiment with each until you get a useful sound. Congrats - you've now created a pretty awesome synth!
Improving the Sound with Effects
Creating Material with Sequencing
Recording your Output
Based on a workshop given at the Currents New Media Festival in 2013 by Darwin Grosse