Synthesis and effects

Question 1

Give an example of a signal flow of a synthesiser?

Answer 1

Arpeggiator - Oscillators - Amp - Filter+Delay - Pan - Effects

Question 2

Oscillator: describe the oscillator of string instruments.

Answer 2

• string oscillates to create vibrations (plucked/bowed = sawtooth)
• fingering shortens wavelength
• A light touch allows the whole string to vibrate, but forces a node
• frets are positioned to help guitarists hit lengths related to musical pitches.

Question 3

Filter: how are sound waves created inside a string instrument?

Answer 3

Vibrations of the string conduct through
 the bridge and vibrate the top plate, creating
 sound waves inside the instrument.

Question 4

Filter: what acts as the acoustic chamber of a string instrument?

Answer 4

A string instrument’s hollow body
 acts as an acoustic chamber, where
 sounds echo and resonate.
- Resonance amplifies certain
 frequencies and attenuates others creating a complex timbre.

Question 5

Amplifier: What else does the resonating hollow body do?

Answer 5

Besides modifying frequency, the
 the resonating hollow body amplifies
 the overall sound, making it louder. 
 (especially low frequencies)

Question 6

Amplifier: how does the hollow body compare to an electric amp?

Answer 6

Compare this to a solid-body electric guitar, which must “pick up” the string vibrations and boost them electrically using an electric amplifier.

Question 7

Effects: What happens as sound waves bounce and echo around the hollow body?

Answer 7

As sound waves bounce and echo
 around the hollow body, some take
 longer journeys than others, and are
 thus delayed, creating phasing
 (chorus) and reverberation effects (commonly added electronically in electric guitars).

Question 8

How was EQ used in the past?

Answer 8

To fix technical problems on tape and LPS (A widely-known example is the RIAA equalisation curve
 used for gramophone records).

Question 9

What is parametric EQ?

Answer 9

Mixers have parametric EQ, which allows the cutoff or centre frequency (and Q) of LPF, HPF and BPF filters to be varied.

Question 10

What do graphic equalisers offer?

Answer 10

Graphic equalisers offer a bank of band-pass filters.

• Fixed-bands common in consumer / DJ equipment.
• Software graphic equalisers offer more flexibility…

Question 11

What was dynamics processing originally designed for?

Answer 11

Broadcasting, in order to protect the equipment (e.g. transmitter)
- Signal strengths need to be limited otherwise
components would be damaged

Question 12

Describe what multi-band compressors do.

Answer 12

Multi-band compressors treat different frequencies differently
- Multiple band-pass filters are used to split the signal into separate
 streams, and processed with separate compression effects.

Question 13

What is magnetic tape less able to faithfully store?

Answer 13

Like frequency, magnetic tape is less able to faithfully store the wide dynamic range found in music.

Question 14

How does the Dolby NR system help to solve this dynamics issue?

Answer 14

One solution is to compress the dynamic range on recording then expand the dynamic range on playback

Question 15

When does distortion occur in analogue systems?

Answer 15

When the speaker cone is pushed (or overdriven) beyond its physical limit. It can be accentuated by damaged (e.g. torn) speakers cones.

Question 16

How does hard clipping distortion occur in digital systems?

Answer 16

When a signal exceeds (and is then limited to) the maximum amplitude represented by the bit-depth.

Question 17

How were early delay effects created in the studio?

Answer 17

Using multiple tape machines:

• One recording and one to playback
• The “delay” resulted from the physical
 distance between the recording 
and playback machine.

Question 18

How does digital delay work?

Answer 18

• A digital delay effect keeps a buffer of the most recent audio in memory, which is sampled to extract and playback previous audio data as an echo.
• The buffer can optionally include the echoes too, creating a feedback loop (re-circulating echo) – with infinite echoes.
• The feedback ratio must be set low to avoid audio overload

Question 19

What was the first digital delay unit?

Answer 19

1970: The first digital delay line, the Lexicon Delta-T 101, is introduced and was widely used in sound reinforcement installations.

Question 20

Give 3 reasons why we use reverb/

Answer 20

• Can be used to add real-world-sounding acoustic characteristics to a dry studio recording.
• Can be used to add depth and presence to a sound.
• Can be used to push a part “into the background”

Question 21

What is convolution reverb?

Answer 21

Convolution reverb enables the use of special recordings (called an impulse response) of real spaces to apply the acoustic of that space to any sound at a later time