Demonstrate two of the three types of modulated short delay effects (flanger, phaser, chorus). Describe how they function and what they are best used for. Be sure to describe the Delay Time, LFO, Feedback and Dry/Wet sections.

The goal of this tutorial is to explain how modulated short delay effects works, in this case, flanger and chorus, and to give you a start point on how to use it in a musical context.

Key Concepts

Comb Filter, is generated by taking the an input signal  and addig a delayed version of it to the original signal.

"The comb filter is a simple recirculating delay line, in which the signal is attenuated (ie. multiplied by some amount less than one) on each cycle. "

"The characteristic of the comb filter is to emphasize the frequency (and its harmonics) of the reciprocal of the length (in time) of the delay line"

Delay Time, it is the ammount of time, usually in milliseconds the original signal will be delayed from its copies. In other words, how long after hearing the original sound the copy of it will be heard

LFO (Low-frequency oscillation), it is an electronic signal which creates a rythmic pulse
and whose frequency is at the bottom of, or below, the audio range. With a LFO we can create pulses that we can apply to our original signal to create a number of effects.

A LFO can generate a variety of useful waveforms, including sine, triangle, square, ramp-up, and ramp-down.The most useful LFOs have an upper frequency limit above 100 Hz and a lower limit below 1 Hz


Feedback, is the ammout of the input signal which is injected back in to the original signal

In the graph we have an input signal (+)  which goes though an effect (A) before reaching the Output, the signal get reinjected with the original input signal.

Dry/Wet,  signal processing units or software have a 'wet/dry' setting which determines the proportion of mix between the original (dry) and 'effected' (wet) signals.

Remember: Dry refers to the unaltered signal.  Wet refers to an altered signal.


How Flanger Works 

Flanger  is an effect that mixes the original signal with a varying, slightly delayed version of the signal. The original and delayed signals are mixed more or less equally. Mixing the original signal with a variable short-term delay creates a series of sharp dips and notches in the frequency response(Comb Filter).

As delay time is shifted up and down by an lfo, a sweeping effect is created.


Speed on the phaser alters the rate at which the comb filter moves through the audio spectrum, depth controls the size of the "teeth" on the comb filtering through the audio spectrum.

Best uses for flanger

Flanging works best on harmonically rich sounds, but it is also strong enough to show up clearly on clean guitar, drums, or even vocals. 


Parameters

Delay Time: Changes the time it takes for the second signal to play after the original. Most times the highest setting will not be more than 20 milliseconds

Depth: This parameter functions as the control for the severity of the changes in pitch.

Width: This parameter is somewhat similar to Depth, but has a noticeable difference to the ear. It controls the speed at which the peaks and valleys of the flange are reached.

Rate: This controls the rate at which the warbles(changes in pitch) repeat themselves. The faster the speed, the faster your audio signal will go through the complete flange process.

Feedback: loops the output signal back into the input, creating a possibly infinite amount of noise.



How Chorus Works

 The idea  is to create clones of the input signal and  then, delay the signal for a few milliseconds, around 15-30ms and also detune (changes the pitch) the copied signal a bit.

Used subtly we get a doubled effect that sounds like many players playing the same part. When pushed to the max, can sound like an intense detuned sound.

Most modern chorus effect unit, be they plugins or hardware based, also spread the effect signal across the stereo field. Sometimes a parameter to control the depth and other behaviours may be encountered.

Best uses for Chorus Chorus is used on many different sounds. Guitar players love it for creating clean sounds. Keyboard and synth players commonly use it to thicken up their sound. For vocals, chorus can help cover up subtle pitch problems. Chorus can also add the illusion of width to a sound, making it appear fuller and wider. Wherever you use chorus, go easy and don't go overboard.


Parameters:

Delay Time:  Controls how long it takes for the second, copied signal to appear. The amount of time is generally kept fairly low—usually between fifteen and thirty milliseconds.

Depth:   Controls the amount of change in modulation or pitch of the sound. The higher the number, the weirder it's going to sound!

Modulation Rate : Controls how fast the pitch will rise and fall. Also sometimes referred to as the LFO frequency. Higher frequencies produce extreme effects. 


In closing

 Try listenging the recordings of your favorite musicians/bands to get a better sense of how to aplly Chorus and Flanger ir a musical context.

For flanger you can listen to Jimi Hendrix´s compositions, you can try with  Voodoo Child

For chorus  you can hear it heavily used in Nirvana´s song Come as you are from , also in the spanish hard rock band Héroes del Silecio, Juan Valdivia(guitar) plays a lot of arpegios and does use a lot of chorus (and also flanger) to thiken up his tone (try Maldito Duende and Sirena Varada) .

Thanks a lot for reviwing this tutotial, hope this was useful for you.