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The following effects are primarily time effects. However, some of them are closely related to the other categories. These effects delay the original sound, add copies of the sound, or add multiple refl ections to the original sound. These effects develop over time and often carry on past the end of the original instance of the sound.

Delay

The time effect used most often, both independently and as a part of other effects and processors, is the delay effect. A

delay holds back a sound in time and releases it at a specifi ed

interval. Typically, the original sound remains unaffected, while a copy is delayed and mixed in with the original. The copy may also be part of a feedback loop that creates multiple copies that are mixed in with the original. These copies are spaced apart and can be timed to any desired tempo.

The delay effect is used for several purposes. The fi rst is to add space around the sound. A delay can emulate how sound refl ects off different surfaces. This emulation can give a dry sound additional depth and realism, placing the sound in a pseudo-reverberant fi eld. A delay effect can also be used to change the sound and give it a larger-than-life quality. The result is determined by the delay time and the feedback amount. A short delay with very little feedback creates a slap

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delay and gives the sound the illusion of a larger sound. A longer delay with a longer feedback adds space around the sound. In either case, experimentation is required to fi nd the sound you are looking for.

If the sound source you are recording has a tempo (like a drum loop), then you might consider using a timed delay that matches the tempo of the source. This helps the delay blend in and can be a pleasing effect. If you want the delay to stand out, then purposely mistiming the delay can accomplish this. A well-timed delay can alter the sound or simply enhance it.

Delays are also used on other effects. As you look through all of the other effects and processors, you should note which of them have a delay component and see how it is related to the delay discussed here. The use of delay in so many other areas demonstrates that the effects/processor categories have much overlap.

Various delay-based effects

This section focuses on the principle behind a group of effects that use delay to obtain their results. These include chorus, fl anging, and phasing. Each of these uses a copied and delayed version of the original signal that is then mixed in with the original to create interesting effects.

When a sound and a copy of a sound are mixed together, they add together and the end result sounds louder. When one of them is delayed, interesting things begin to happen because of phase cancellation and boosting. The delay can even be set to follow an LFO (low-frequency oscillator), which changes the delay based on a cycling oscillator and can create interest- ing pitch variances.

These types of effects are almost always used as creative effects. Sometimes, instead of pitch shifting a sound, you might use one of these to camoufl age pitch problems.

Audio Sampling

Reverb

One of the most often used time effects is reverb. This effect emulates acoustic refl ections that are added to the sound as a way of adding dimension. Reverb units have a set of stan- dard parameters that relate to specifi c acoustic equivalents. These parameters include the direct sound from the source, the initial refl ection, other early refl ections, general reverb, and decay time (Figure 5.7). A reverb unit attempts to re- create this process using a complex series of repetitions of the sound source. Most reverb units have a basic algorithm that defi nes the fundamental space of the emulation. This might be a specifi c room, a cathedral, or a concert hall. The pre- delay setting defi nes the time between the original sound and the fi rst refl ection. Increasing the time on this setting increases the perceived size of the room. There is also a decay setting that lengthens or shortens general reverb time. Other settings such as equalizers and modulators vary from reverb to reverb, but most reverbs do have additional and useful features. Another way of setting reverb parameters is based on convo- lution. This type of reverb creates highly realistic replications

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of specifi c locations, because the source material of the unit comes from those specifi c places. A set of microphones and a speaker are set up in a location that is to be captured. A sweeping sine wave is broadcast through the speaker and is captured by the microphones. The microphones capture the sound of the sine wave in the room. The resulting sound fi le can be decoded using the recorded sweeping sine wave from the room and the original sweeping sine wave. The sine wave is effectively removed, and a fi le called an impulse response is left which can be used in convolution reverb units instead of a more traditional algorithm to create the basic sound. An alternative method of capturing an impulse response uses a short sound burst, commonly a balloon burst or starter pistol. While these are easier to use, they provide less accurate results.

Reverbs can be used in much the same way as the delay effect discussed earlier. They can be used to create a space around a sound or the give the illusion that the sound is bigger than it really is. This is accomplished by adjusting the basic reverb parameters/impulse response and the decay time. If the basic reverb is set to a large room but the decay time is set very short, then the source will sound larger without sounding like it is in a large room. If the decay time is lengthened, then it will sound like it is in a big room.

Reverb units also have equalizers built in. An equalizer is a frequency-specifi c volume control. Using an equalizer can help achieve natural results. The sound passing through a reverb unit is often varied, and the reverb doesn’t always suit the sound. An equalizer can be used to smooth out frequen- cies that do not sound natural or boost frequencies that are lacking. In either case, equalizers are used enough that they are now a part of nearly every reverb unit. See the equalizer subsections in Section 5.4.2 for more information.

Reverb units are used in a multitude of situations, but there are times when they should not be used. It is important to know when those times are. When your sampled instrument

Audio Sampling

is fi nished and it gets used in a recording session, most likely it will be passed through a reverb as a part of the mix. In this case, it might be desirable to have a dry sample with no reverb or delay. If you use reverb on the sample, then when it is mixed with other reverbs later, either by you or some other end user, it might not sound good. In later mixing ses- sions, the engineer might have a specifi c sound in mind that could clash with the reverb on the sampled instrument. On the other hand, if your sampled instrument has a specifi c sound that is built around a specifi c reverb, then including the reverb is a requirement. When it is used later, the engineer has to take the reverb sound into consideration. Don’t be afraid to add reverb to the source, but if it is not necessary, you might consider leaving it off completely. Another option is to create two versions, one with reverb and one without reverb.