1. Signal Processing (time-based effects)
Delay, Modulation and Reverb effects

2. Why do we process sound for recordings and live music performances?
Signal processing is used to mold and shape the sounds that are used in an audio recording.
All commercial recordings and professional live performances make extensive use of signal processing.

3. basic rules that relate to sound processing:
Effects are best employed when the user actually understands what the effect really does to the sound.
Don’t over process sounds unnecessarily
(less is more)
Applying effects should not make up for poor microphone technique and equalization
Effects will not substantially improve a weak composition, arrangement or performance.

4. Effects processors can be hooked up in three different ways:
In-line: The signal is sent directly into the unit from an instrument and then right into a mixer or amplifier.
Effects loop: Connection to the send and return (effects or aux) bus on a mixer or amplifier. This method is used if we want to add the same effect to a variety of different channels or parts at the same time. Example: Reverb
Insert: Inserted into a channel strip of a mixer.

5. Typical signal path: Source Microphone Instrument (DI) Equalization
Parametric EQ
Graphic EQ
Wah
Dynamic Processor
Compressor
Modulation Effects
Chorus
Flanging
Phasing
Rotary
Spatial Effects
Delay
Reverb
Dynamic Processor #2
Volume Pedal
Noise Gate

6. There are three main types of time based effects:
Delay
Modulation
Reverb

7. DELAY
A delay unit records a sound and then reproduces the sound a little later.
Delay gives the listener the impression that the sound is being made in a larger environment. This is referred to as delay time or delay length. Delay time is usually measured in milliseconds (ms).
There are 1000 milliseconds in a second.
In the early days of recording delay was created with tape loops. These days delay effects are created digitally.

8. The Three Basic types of delay:
Slap Back
Doubling
Repeated Delays

9. SLAPBACK The simplest form of delay
Slapback is a single repeat of a sound (35 ms to 300 ms).
This effect is most commonly used to thicken a vocal or instrumental part.

10. DOUBLING
A doubling effect is created when delay time is set to less than 35ms.
This gives the impression that two people are performing a part in unison.
When doubling always use prime numbers for delay times (ex. 1, 3, 5, 7, 11, etc). This yields better results when a recording is heard in mono.

11. REPEATING DELAYS
Repeating delays are achieved with the use of a regeneration control dial (feedback).
This dial feeds the delay signal back through the unit.
The higher the feedback the greater number of repeats.

12. Calculating Delay Repeats
Delay repeats should line up with the rhythmic groove of a song.
There is a simple formula to calculate the delay time that will repeat in quarter notes along with the tempo of a song.
 bpm (beats per minute) = delay time per beat (quarter note) in milliseconds

13. Tempo in Beats per Minute
Delay Time Table:
Tempo in Beats per Minute
Quarter Note
Eighth Note
Sixteenth Note
Quarter Note Triplet
Eighth Note Triplet 20
3,000
1,500
750
2,000
1,000 25
2,400
1,200
600
1,600
800 30
500
1,333
667 35
1,714
857
429
1,143
571 40
375 45
333
889
444 50
300
400 55
1,091
545
273
727
364 60
250 65
923
462
231
615
308 70
214
286 75
200
533
267 80
188 85
706
353
176
471
235 90
167
222 95
632
316
158
421
211
100
150
105
143
381
190
110
136
182
115
522
261
130
348
174
120
125
480
240
320
160
154
135
111
296
148
140
107
145
414
207
103
276
138
133
155
387
194 97
258
129 94
165 91
242
121
170 88
118
175
343
171 86
229
114
180 83
185
324
162 81
216
108 79
195 77
205
293
146 73 98
210 71

14. Modulation
The modulation control on a delay unit is used to create other popular effects such as chorus, flanging and phase shifting.
These effects involve pitch variations that are created with a LFO (Low Frequency Oscillator) that continually varies the delay time.
Altering the range of delay time (depth) and the speed of change (speed) will create a great variety of modulation effects.

15. Phase Shifting
Phase Shifting occurs when a delayed copy of a sound is heard directly after the original.
The two sounds are so close together that they almost cancel each other out.
This is known as phase cancellation. To achieve this effect the delay time is set from 0.2-2ms.

16. Flanging
Flanging is a metallic effect that was originally created by playing two reel to reel tape recordings of the same tune simultaneously.
The engineer varied the speed of one of the tapes by touching the edges of the reel (“the flange”).
This created a short delay that varied anywhere from 10-20ms between the sounds. It is best used on Rhodes pianos and guitars.

18. Chorus
Chorus attempts to simulate the time and pitch variation of a choir.
This works well on background vocals, guitars and keyboards.
The delay time is set anywhere between 15 and 35ms.
With the longer delay time we actually hear a noticeable pitch variation.

19. Enhancing modulation effects
All of these modulation effects can create even more interesting results when they are used in stereo.
Most modern effects devices are available in stereo.
Quite often they will even turn a mono signal into a stereo processed sound.

20. REVERBERATION Reverberation is really just a series delays.
Reverb devices attempt to simulate the sound of a specific acoustic environment.
Basically every modern recording and most live performances make extensive use of reverb to help make the music sound larger than life to the listener.

21. Variables (dials) that can be altered on a reverb device to simulate an environment:
Pre-delay: time delay that happens before the reverb is heard.
Reflections: the number of times that a sound bounces around a room
Diffusion: amount of time between the reflections
Decay time: the amount of time it takes for a sound to decreases to one millionth of its original sound pressure level.
Density: the time spacing of the initial reflections.

23. Most Common Reverb Settings:
Hall: smoothest and richest
Chamber: echo chamber
Plate: bright
Room: bedrooms to large conference rooms
Reverse: backwards effect
Gated: lots of reverb that is closed off quickly
(Phil Collins drums)