Electronic music - audio effects
Contents
Noise gate
Compressor
Multiband compressor
Distortion, overdrive, fuzz, etc.
Delays and reverb
Some relevant theory
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Relevant is the precedence effect a.k.a. Haas effect and the law of the first wavefront, which roughly says that due to our binaural ears, we have learned to hear similar sounds that come very quickly after each other as, well, not separate sounds.
Similar sounds coming in up to approximately 30ms apart are heard as a single sound,
and can often be used for localization.
Anything further apart in time becomes heard as echo, or just separate sounds.
This is also useful information for mixing music, e.g.
- if you create have two copies of the same track, one delayed on the order of 0.5ms, panned differently,
- these will sound a little more spaceous
- create depth in mono tracks
- e.g. by doing the above trick on hard-panned duplicates, and possibly with longer delays
- reducing directional masking
https://en.wikipedia.org/wiki/Precedence_effect
https://en.wikipedia.org/wiki/Sound_localization
Flanger, Chorus, Doubling
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Chorus, flanging, phasing, (also reverb, but that's a wider topic) feel mainly like changes in texture, due to being shorter-than-30ms delays.
Flangers usually stay within 1..5ms delays (but maybe up to 20ms?(verify))
- ...because phase effects will dominate with small delays
- The result is a much like a comb filter, creating frequency attenuations with harmonic relations, and tuning the delay causes these attenuations to shift.
- Named for tape flanging, where two recorders would record the same sound, and you would play back and introduce a delay by momentarily putting some friction on the reel flange (the rim that holds the tape in) of one of them.
Chorus and doubling both refer to having two sounds of the same pitch, comparable timbre played at the same time.
Doubling frequently refers to using distinct repdorductions of the same thing.
- happens around 20..40ms (high enough to avoid phase effects, low enough to not quite become heard distinctly)
As an audio effect, you can get something similar(-but-often-clearly-cleaner) by exact(ish) reproduction with a small delay. Phase effects are usually irrelevant because of the somewhat larger delay.
There is a preference for having multiple performances of the same thing, aligned closely - the small inconsistencies will be perceived to add to the timbre, which sounds fuller and more natural. In a home studio this you can play or singing the same thing. Some string instruments have doubled strings of the same tuning (but never perfect) which gives a similar effect. Orchestras (in particular strings) and choirs get this just with multiple people trying to do the same thing.
Chorus
- on the order of 5..30ms
- aiming more for doubling effect, and less phase effect than flanging
- often for a fuller sound, and could e.g. be used to create a spatial-seeming stereo effect from a mono source
Can refer to a more controlled effect, e.g. from a pedal or a synth, which can have a more shimmering quality due to more consistency, leading to beating frequencies and phase-related details.
Chorus as an audio effect often adding a delayed copy (5-25ms(verify)), possibly slightly pitch-modulated to get some beat frequencies.
Synths also sometimes do this by sending the same commands to slightly differently tuned oscillators.
Chorus has other uses, such as a little hiding of tuning imperfection, since intuitively accept a wider frequency band as a the intended instrument.
...and yes, the distinction between chorus and doubling is sometimes fuzzy.
Above 40ms things clearly start to separate, above maybe 100ms it is more clearly distinct and we'd call it things like echo.
https://en.wikipedia.org/wiki/Chorus_effect
https://ccrma.stanford.edu/~dattorro/EffectDesignPart2.pdf
Echo and Delay
| This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me) |
Delay, as an effect, is a single copy some time later refers to keeping hold of a signal to play back a little later. So like echo, but just one.
Probably the first delay was tape delay, using the distance between record and reproduction head to get just one copy.
This was often on the order of 40-200ms, often around 100(verify).
Such delay delays, on instruments that sustain at least a little, are extra playing that you can tell apart if you focus, but sound like doubling sort of sustain effect if you don't.
From that view on delay, echo is longer delay that you can tell apart, with our without feedback.
Echo could be considered a delay effect that feeds back into itself, so has a sound repeat at a regular interval and decreasing volume (and often fidelity).
Delay effects with feedback often attenuates the high end, because without that they tend to go crazy and screechy with stronger feedback (near unity gain).
30-50ms of delay might be called doubling echo, walking the line between the two
70ms+ with little or no feedback is called slapback echo - an effect used e.g. on fifties guitars, and things like rockabilly.
Delay is sometimes used for non-musical purposes.
Delay without furter effects is used to compensate for distances in PAs.
https://www.uaudio.com/blog/modulation-effects-basics/
Tape delay
Delay ICs (and DIY)
BBD and Digital delay DIY
DIY Spring reverb
See also
spring reverb tank coding
Physically, reverb tanks are mostly
- a small voice coil,
- different springs (often two or three of them)
- a pickup coil (or sometimes piezo)
In terms of electrical impedance, you could think of it as a small speaker, and a small pickup.
Impedances will vary between types; input between a few Ohms and maybe a kOhm, output a few kOhms. You can tell from the code (accutronics started, most follow).
Codes:
- number: usually one of:
- for Accutronics:
- 1: 9.25" (~23.5cm), 2 springs
- 4: 16.25" (~41.3cm), 2 springs
- 8: 9.25", 3 springs
- 9: 16.25", 3 springs
- for Belton:
- 2: 2 springs
- 3: 3 springs
- for Accutronics:
- letter: input impedance at 1kHz (ranging from 8 Ohm to ~2kOhm)
- A: 8 Ohm for Type 1&4, 10 for Type 8&9
- B: 150 Ohm for Type 1&4, 190 Ohm for Type 8&9
- C: 200 Ohm for Type 1&4, 240 Ohm for Type 8&9
- D: 250 Ohm for Type 1&4, 310 Ohm Ohm for Type 8&9
- E: 600 Ohm for Type 1&4, 800 Ohm for Type 8&9
- F: 1.4 kOhm for Type 1&4, 1.925 kOhm for Type 8&9
- letter: output impedance at 1kHz
- For Accutronics:
- A: 500 Ohms for Type 1&4, 600 Ohms for Type 8&9
- B: 2250 Ohms for Type 1&4, 2575 Ohms for Type 8&9
- C: 10000 Ohms for Type 1&4, 12000 Ohms for Type 8&9
- For Belton:
- A: 500 Ohms for Type 1&4, 600 Ohms for Type 8&9
- B: 2250 Ohms for Type 1&4, 2575 Ohms for Type 8&9
- C: 4000 Ohms for Type 1&4, 4000 Ohms for Type 8&9
- D: 10000 Ohms for Type 1&4, 12000 Ohms for Type 8&9
- For Accutronics:
- number: decay time
- 1: Short, (~1 to 2 sec)
- 2: Medium (~2 to 3 sec)
- 3: Long (~3 to 4 sec)
- letter: grounding/shielding - mainly about ground loops (so buy to match what you're replacing, though various cases are fixable afterwards)
- A: input connected to chassis, output connected to chassis
- B: input connected to chassis, output isolated
- C: input isolated, output connected to chassis
- D: both input and output isolated
- number: travel lock (now rare, meaning it's usually 1)
- letter: mounting plane - basically which side is up
- A = Open Side Up
- B = Open Side Down
- C = Connectors Up
- D = Connectors Down
- E = Input Up
- F = Output Up
- this is mostly about which direction the springs are off-center to avoid hitting things, and best distance to the magnets? (verify)
If replacing one in an amp, you
- likely want to match the impedance
- probably want to match the grounding and mounting plane.
- want to match size if larger won't fit.
- you have some leeway in spring amount and decay and size, if you want to experiment.
See also:
Repurposing a floppy drive as sampler or tape-style delay
Reverb
Presence
Wah-wah
Talk box
A talk box is just a box with a speaker, and a hose that puts that sound in your mouth.
Your mouth effectively makes vowel-like resonances, to be picked up by your vocal mic. Seems to have been mainly used for guitars.
https://en.wikipedia.org/wiki/Talk_box
Bit crusher
Vocoder
Autotune
Phase shifter
Pitch shifter, frequency shifter
Modulation
Modulation alters a signal waveform using a carrier waveform.
https://en.wikibooks.org/wiki/Sound_Synthesis_Theory/Modulation_Synthesis
