Tape Delay

The first delay was created using a tape machine. The following is a drawing of the tape path in a typical tape recorder.

The tape first passes the erase head that wipes the tape. Then it passes the record head where the signal is put onto the tape. Finally it passes the play head where it is played back. The time taken for the tape to pass from the record head to the play head determines the delay. If the tape recorder is going fast the delay will be short, if slow the delay will be long. The speed of the tape is determined by the speed the capstan motor is turning and in the early seventies the tape machine manufacturers started to add variable speed motors with a control called varispeed. Using this you could set the delay (by ear) to the appropriate speed. If you took the output from the play head and fed it back into the input of the recorder you would get repeat after repeat as it cycled around. As only a small amount of the first delay was fed back it would continue round the loop dropping in level each time and the classic delay was created. This control was called Feedback.

If you were using a stereo tape recorder you could have stereo delay. If you put in a mono signal you got out a mono delay because each side of the delay was the same. Thus:

Which sounded like this visually!

Click on the Image to hear the sound

Because both sides have the same signal the delays sound mono in the centre.

Enter the Digital Delay Unit.

Digital Delay

The digital delay unit changed everything. Firstly you could dial up the delay you wanted but more importantly you could vary the delay of the left and right sides. So if you put in a mono signal and set the left side to 500ms and the right side to 250ms, applied some feedback and you ended up with a delay in which the left side was different to the right side and true stereo delay was starting to be a reality.

Example 1 Click on the Image to hear the sound

I hope you are following me here - what I'm trying to do is to get you to picture the delays as they would be heard. On the left side we have a 500ms delay while the right is at 250ms. Every 500ms the left and right delays are the same - therefore the sound comes from the middle. What you think is stereo really isn't, what you are wanting is something like this:

Example 2 Click on the Image to hear the sound

Or this

Example 3 Click on the Image to hear the sound

or this!

Example 4 Click on the Image to hear the sound

This is where the understanding of what makes things stereo and what is mono is extremely important. The thing that makes a sound come from the left can be more than just it being a mono signal coming from the left. It can be a stereo signal, where the left is different from the right, yet appears to come from the left. If we were to set the delay so that the left delay is 510ms and the right is 490ms the delays would be 20ms apart, right? If two sounds are 20ms apart or greater they sound like two different signals left and right - so if two delays are 20ms apart then they should sound as though they come from left and right. Thus:

Example 5 Click on the Image to hear the sound

Sure the left delay will be 20ms later every delay but in 4 delays that's only 80ms out of 510ms and remember relative to the beat one delay starts 10ms ahead whilst the other is only 10ms behind. Try it with a track as you'll see what I mean.

Another way to make each side dissimilar is to change the pitch of one side or both sides. I created Example 3 by doing just that - I changed the pitch of one of the sides so even though they are in time they appear as stereo because they are dissimilar.

I created these delay sounds using a Multi-Tap delay. Instead of using feedback to create the repeats as with tape and straight digital delay, in a Multi-Tap Delay you can control each delay. If you imagine that each delay is a Tap, you can set what each delay will be at each tap - even where it is panned. This is much more extensive a control of the delays than using straight feed back where each delay is just a repeat of itself.

You can see how I've played around with aural visualisation and that's what the guys and gals who make all those incredible delay programs do all day. Next time you get one out try looking at the sound it makes and picture what's going on instead of just listening to it.

sound has depth,height,breadth

Setting the Delay time

Setting the delay time depends on the Tempo of the track you're recording. If the tempo is 120 beats per minute there are 120 beats in 60 seconds or 120 beats per 60,000 milli seconds which is one beat every 500 milli seconds. So with 4 beats in a bar, quarter beats are 500ms, eighths are 250ms, sixteenths are 125ms etc. So how do you find out what the delays are if you know the tempo? There are some computer programs like Beat Calc that will automatically work it out for you, some of the new delay units and programs have a tap function that allows you to tap in a tempo and the device will work it out and you can get charts with it printed out. They will not only tell you what the 1/2, 1/4, and 1/8th beats etc. are but will also tell you the dotted note delays and the triplet delays. I've created a chart for you called the Tempo Chart

Quick Delay Calc

There is a quick way you can work out the delays of a track using a stopwatch that reads 100th of a second.

Play the track and start counting the quarter beats. Then start the stop watch on the beat and count ten quarter beats and stop the clock on the eleventh beat. You will get a reading like:

Thus a quarter note beat will be 460ms, an eighth will be 230ms and sixteenth will be 115ms etc. This is a handy technique if you are a PA mixer and you want to put a delay on the vocal and you quickly need to work out the tempo the band is playing at.

 

ENTER THE MODULATORS

The Phaser/Flanger

When a jet flies over, you hear it coming and its sound is going up in pitch - then when it goes away its pitch drops. This effect is called the Doppler Effect. If you had a very tight delay of 10ms but could change it using a modulator so it varied from 0ms through to 10ms and back to 0ms etc. sweeping forward and back relative to the original signal. When the delay is increasing the phase shift is increasing and the doppler effect will cause the sound to lower in pitch like the jet flying away and when its modulating back and shortening the delay the phase shift will cause the pitch will rise like the jet coming towards you.

That is the classic phaser sound. The effect was originally created on short wave radios where a receiver was picking up a signal that had come around the world one way as well as another longer way and when the two were added together at the receiver they added and subtracted from each other causing the phase shift or Comb Filter Effect that creates the sweeping pitch effect we now associate with phasing, and which is also why they are called phasers. Phasers shift the phase relationships within the sound using phase shift circuits. Flangers are the same sort of thing, except that flangers use time shift circuits to obtain the effect. The modulator has controls like

The Chorus Unit

If you increase the delays from the 0 - 10 ms area and go out to the 60ms - 80ms delays but still modulate the delays the effect changes to the Chorus effect.

The guitar in this track has the classic chorus guitar sound most of which was created using the classic Roland Dimension D, in fact there were two of them. The modulation rates are usually faster than phasing but the depth is a lot less so there is only subtle change going on. If you look at the controls on a chorus unit you will find the same controls as in phaser units, Delay - Depth - Rate - Feedback - Shape. You can set the delay on a chorus to be in time with the track so if the tempo is 120bpm the 16ths are at 125ms and the 32nds are at 62.5ms - or you could try 62.5ms and 31.25ms as well. It really makes a difference.