Some of the most powerful tools we have as recordists are time-based effects: delays (echo), choruses, flangers, phasers and doubling. A well set delay or chorus can add exitement to a mix and can create a monstrous groove. Inversely, if your effect is set to the wrong time, it can completely destroy the feel of the music or mess up an otherwise tight composition. Lets look at why this happens and how we can control it effectively.

What is delay?
Simply put, it's an echo. If you add a delay to the guitar part of a piece of music, it repeats the original sound one or more times, adding more notes at later times than the original - it's like having a second guitarist play along with the first. However, if the delay time is set incorrectly, the new notes fall in the wrong places, out of time with the beats of the music. Now, I'm sure you all know what it sounds like when one member of a band doesn't play in time with the rest - chaos. With an errant band member we either: live with it; make them practise (possibly by hitting them repeatedly - call it percussive education); or replace them. With a delay it is easier - change the delay time. To know what to set, we need to understand how note values relate to delay times.

Note Values as Time
The beat or pulse of a piece of music is directly related to time. At 60 bpm (beats per minute) there are 60 beats every 60 seconds, or to simplify, one beat per second. If the music is in 4/4 time, this means that the time value of a quarter note is 1 second - which can also be expressed as 1000ms (milliseconds). An eighth note in the same piece of music is 500ms and a 16th is 250ms. To get a bit more complex, a dotted quarter note will be 1500ms and a Quarter note triplet will be 666.6ms.

Calculating Correct Delay Times
In the above example of 60 bpm, it's easy to work out the correct note values as 60 seconds divides neatly into 60 beats. But what happens when you have 65 bpm? Or 80? Now we need something to help us work out the delay times (unless you have a pretty good mathematical ability).

Firstly there are books filled with tables, giving all major note values expressed as milliseconds at most common tempos (usually 60bpm to 240bpm). This is the way us old folks used to do it way back when... These are now freely available on the Internet too, so feel free to fire up Google and do a search.

A much easier route is to use a Delay Time Calculator - also freely available on the Net. In fact, I'm posting one on this site this month. Just follow This Link... It'll open in a new window, so don't be scared now!

Other Delay Time Niftyness
Play around with delay times by changing them to a few milliseconds faster or slower than the exact note value and see how they change the feel of the track, either "pushing" or"dragging" it. You may find it does just what you are looking for.

Other effects that are time-based can also benefit from our new found knowledge:

Phasing Type Effects - (Phasers, Flangers, Choruses - anything that goes "whoosh") - It's nice if these effects can start a cycle at the beginning of a beat and end at the finish. To do this just set the rate control to one of the note values. Rate is often expressed as Hz (cycles a second) and if you have a look at the Delay Time Calculator, you will see that it includes this too. Getting a bit more complex, if you want to have the cycle begin and end with a full bar of music (a la '60's phaser), halve the half note value to get your whole note value and then divide by your number of beats to the bar. In our example of 4/4 timing at 60bpm, this results in 0.5 Hz / 2 /4= 0.0625Hz.

Reverbs - the "pre-delay" that any decent reverb has, is a simple way of clarifying a reverb effect, making the resulting sound less cluttered. It does this by introducing a short wait before the reverb occurs. This allows the original sound to stand out a little more. While pre delay is usually very short, making the setting of it less crucial than that of a distinct echo type delay, setting it to a related note value does make the reverb "punchier" and more precise. A common trick on better rreverb units is to chorus the reverb sound to make it more natural - so you can follow the rate trick mentioned above for the chorus too.

This is Your Final Warning
One thing about nicely synched delay times is that because everything is so nicely and precisely lined up, the delays do not get in the way of the track. While this is A GOOD THING (TM), it's quite easy to get carried away and apply to much effect to your mix. We've all been THERE, and most of us learned our lesson and don't want to do it again.