Sounds?

How do we make interesting sounds with the microbits?

Digital Synthesis Approaches

• Additive synthesis
• Subtractive synthesis
• FM (frequency modulation) synthesis
• Envelopes and ADSR
• Drums: noise and non-pitched sounds
• Wavetable synthesis

What’s digital sound?

Digital Sound

• Monty Montgomery: Digital Sampling Youtube, Direct Video Download
• Technology Connections: Nyquist-Shannon Youtube
• Computerphile: How Digital Audio Works YouTube

What’s an Oscillator?

• A module (physical or code) that outputs a waveform.
• In synth lingo, sometimes a VCO (voltage controlled oscillator).

Additive Synthesis

• Take multiple oscillators and add them together!
• Some people are trying this in Assignments 1 & 2
• Need lots of oscillators to make complex sound.

Subtractive Synthesis

• Use one oscillator and take sound away.
• We use a filter to remove sound.
• One example of a digital filter is the n-sample moving average filter.
• Subtractive synthesis is typical for analogue synthes (e.g., Korg MS-20).

FM synthesis

• “frequency modulation”
• Use one oscillator to control the frequency of another.
• Cool sounds with few oscillators (see Yamaha DX7)

Let's make some sounds!

Amplitude Envelope

• Amplitude is the “volume” of our note.
• Envelope is the chunk of time for our note to exist in.
• We can change the amplitude over the envelope to give a note a sonic “shape”.
• In synth lingo, an EG (envelope generator) makes envelopes.

ADSR Envelope

• The adsr shape is often used for pitched sounds.
• ADSR: attack, decay, sustain, release

Drums and Percussion

• Are drums all “non-pitched” sounds?
• Start with noise, or combine inharmonic frequencies.
• Percussion envelope? Short attack, no sustain, moderate to long release.

Let's make some notes!

Wavetable Synthesis

• Save the samples for a single cycle of a waveform in an array.
• Step through this array to over and over to play back the sound.
• How do you change pitch?

Further reading

• VCVRack - free “analogue” modular synthesis software.
• Powerful “digital” synthesis: Pure Data
• ANU Laptop Ensemble (it’s a real course!)
• How to get started with Pd (Charles YouTube).
• Installing Pd on your laptop.
• Charles’ computer music intro with Pd

More fun things

Too many oscillators: Look Mum No Computer

How old school game music worked

Questions