Bobby Nathan's

Keyboard Magazine "In The Studio"

Article # 6


By Bobby Nathan

Long before there was midi... There was echo, delay, phasing, flanging, and chorusing. Part of a good engineer's reputation and a keyboard players trademark sound were based on the subtle and sometimes not so subtle use of the above mentioned effects. All of the above mentioned effects were, for the most part, obtainable only in the studio. Later, as devices like the echoplex, the Binson Echorec, the Guild Copy Cat and the Roland Space Echo came into play, many musicians could afford and make good use of these effects. Even though reverb was on the scene as a standard feature included with many guitar amplifiers and organs, reverb never excited the player and listener the way echo units did. I would to focus on echo in this article and go into depth about reverb in a future article.

First, I would like state my definition as to the differences between echo and delay. I've always thought of a single echo to be a replication of the original sound but with a distinct frequency curve. In this curve many of the lo-mid and midrange frequencies are boosted and the high frequencies attenuated. A single or multiple delay in comparison, is the original sound duplicated exactly without any sound coloration. Obviously a delay can be much more flexible than an echo, as a good starting point to "synthesize" ambience because it is relatively flat to begin with. In general, I've always thought of echo as having more that one repetition and delay having primarily one.

Early echo units were in reality, tape recorders. They had either a movable record head or a playback head. The length of the echo created was dependent on the distance between the two heads divided by the speed at which the tape was moving. Mastering the use of echo with tape recorders required a good ear for approximating the actual length of the echo. Most digital delay units have solved this problem by displaying the length of the delay in milliseconds. Knowing the right amount of delay to use is essential in createing the right "echoed or delayed" effect. For example, if you are trying to use a quarter note delay that is faster in tempo than that of the song of which it is added to, this will produce a very "anxious" type of psychological effect on the listener. Good for tension music. On the other hand, a slower in tempo 1/4 note delay will create a more layed back feeling. Great for ballads. And lastly, delaying an instrument perfectly in time with the track, will have no other effect on the listener other than the amount of ambience created. So as you can see knowing the right or the wrong use of echo and delay can definitely have its advantages.

A simple formula that we use at Unique Recording to calculate the length of various musical delays was conceived by one of our senior staff engineers, Frank Heller. It is as follows : based on the theory that there are 1000 milliseconds in a second or 60,000 milliseconds in a minute, by dividing 60,000 milliseconds by the number of beats per minute of the tune one can figure out the length in milliseconds of a quarter note echo.

see example:

60,000 milliseconds ___________________ = number of milliseconds of delay for a 1/4 note delay Beats per minute

Other note values can be calculated by dividing or multiplying the length of the quarter note echo. It then a simple affair to set your digital delay to the appropriate delay time.

Creating echo with a digital delay unit is yet another matter. As I stated earlier, an echo has a distinct frequency curve. Because a digital delay is close to being flat in frequency response, digital delay is a very unnatural sound. It's unnaturalness definitely has its place in todays sound, but to synthesize a natural environment using a digital delay, one must have a good ear, a good understanding of length of delay in relation to the length of the room and a good idea of what frequencies are boosted and attenuated in various environments. A basic formula for length of delay in relation to the distance of the wall in the room that the echo is bouncing off is as follows: on the basis that sound travels at 1100 feet per second or 1000 ms, if we divide 1000ms by 1100 feet we surmise that 1 foot equals .91 milliseconds. So if you multiply the distance in feet ( from where the object creating the sound is to the wall that it is echoing off ) by .91, the result is delay time in milliseconds.

example shown :

Distance in feet x .91 milliseconds = delay in milliseconds

Small rooms with carpeting and upolestered furniture will obviously have very short echo times. If any and whatever echo is present, it will have very little high frequency. Larger rooms with less floor and wall treatment in respect will have more high frequency response. For example a large wood and concrete gymnasium will have a boosted lo-mid and midrange curve with a slightly attenuated high frequencies.

What this all means,is that for one to synthesize a natural echo, equalization will have to be used. Most digital delay units have high frequency rolloff settings but their effect is limited in helping create a more natural echo. With natural echo, where there are more than one echoes present, each additional echo has a high frequency response that is less than the one before it. To synthesize these types of ambience successfully, you'll definitely need a mixer. If you are using a keyboard mixer try returning the output of your delay unit to an unused channel on your mixer. Turn the mix control on your delay unit to the "delay only" setting and use the equalizer in the channel you are returning the echo to to equalize the delay. Use the same echo send on your mixer that you are using to send the instruments to the digital delay as your feedback control. In this way each additional repetition will have a diminishing high frequency response. A spiraling type effect can be created by adding high frequencies instead. But be careful for you can easily have serious feedback, with any feedback loop.

Most digital delays have an LFO section that is represented usually by speed, depth and waveform controls. By using short delay times, small amounts of feedback and the LFO section, various flanging and chorusing effects can be obtained. The speed control is self explanatory as so are the depth and waveform controls if you're familiar with synthesizers. It's all in the actual delay setting (sometimes as small as .01 milliseconds) and the amount of feedback with respect to the depth control of the LFO section that can create many variations to the flanged or chorused effect. Equalization in the feedback loop will also change the effect greatly.

Whether you're using echo, delay or any other time related effects, balance is the key to realism. When trying to synthesize a natural ambience keep in mind that the echo or delay is never louder than the direct signal. If your keyboard mixer is stereo and your stage setup is too, try panning different instruments left or right and their echo and delayed returns opposite. This can best be acheived on a mixer that has two different effects sends and only if you have two different echo or delay units. If you've got the gear, try setting the delay times different more even more dimension. If you are returning your echo or delays into channels try this : Send 1 feeds delay one, send two feeds delay 2, when you return delay 1 into a channel pan it to the left, send some of delay 1 to delay two via send 2 and visa- versa return delay 2 to a channel and pan it right and etc. This makes for a great ping-ponging effect.

One effect that today's low cost digital delay units have not parralelled are the effects that the multi-headed tape delay units create. Because the heads are not symmetrically placed, when feedback is applied, the effect produced is many multi- tapped echoes at different timings. This effect is so "unique" it pays to sacrifice the added noise and limited frequency response of a tape delay unit for the quality of the effect.

Anyhow it all boils down to fattening up the sound of your keyboards. Some of the newer midi delay units have presets to recall your favorite echo and delay patches as well as the ability to change delay patches as you select program changes on your midi synth. This is great for a standard chorus with a rhodes patch and then instantly a 1/4 note repeating echo effect when you call up a solo synth patch.

Next month I'll discuss pre-delay and its use with reverb. Until then : GOODBYE...GOODbye...goodbye...?

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