It's been a while since we looked at reverb applications and a lot of new products have materialised in that time, bringing digital reverb within the reach of more readers.

Firstly. Why all the fuss, just why is reverb so important?

To start at the beginning, the first thing to appreciate is that nearly all the sound that we hear in everyday life is reflected sound. This may not be readily apparent, but if you were to visit a completely dead room such as an anechoic chamber, you would find that the level of perceived sound, such as normal speech, was much lower and that it sounded unnaturally dry. When we talk of reverb in the context of recording, we tend to think of a recognisable effect but even the average domestic room has its own reverberation characteristics, though you may not be conscious of the fact. Reverberation can be used to give a sense of spacial identity to a dry sound without being perceived as an effect and, in the context of the recording studio, it can be added artificially to make a dry or synthesised sound more natural. This is particularly important in the studio as there, sounds are generally recorded as dryly as possible, and of course, synthetic sounds have no natural ambience at all. By choosing a short decay time of less than 400mS, the treated sound will take on a sense of identity and reality without seeming to be effected in any obvious way. Because sound reflects from all surfaces, the reverberant sound is in stereo, even if the original sound is monophonic, which is often the case. After all, the sound from a human voice or a violin comes from more or less a single point. Stereo sound sources would include instruments such as pianos, drum kits and so on.

Ingredients

Before proceeding, it's worth looking back over the basic ingredients of reverb.

The first thing to examine is pre-delay; ie. the time between the direct sound arriving at the listener and the first reflections which follow. These early reflections are often discernable as separate echoes but they rapidly buildup into a dense clutter which decays as the sound energy is absorbed by the surfaces that it encounters. As these surfaces tend to absorb some frequencies more readily than others, the reverberation takes on a unique colouration peculiar to each location, and you will have noticed that modern digital reverbs offer a choice of typical room types ranging from bright sounding tiled rooms to long, booming halls. So great is the choice that it may seem bewildering at first.

Before moving on to specifics, here is a solution to what is a big problem for those limited by the number of tape tracks at their disposal. Budgetary restrictions usually limit the home user to only one reverb unit; even £395 for a Midiverb can be a lot of money to the home 4-track user. However reverb sounds far better in stereo than in mono, yet if you add it all during the mix to achieve this, you are limited to one setting when you may want to use several. Conversely, if you record the reverb onto tape as you put the tracks down, you can choose any setting you like but you can't afford to use enough tracks to keep it in stereo. What you finish with is a mono mix of the dry and reverbed sound on one track, so what is the answer? A compromise solution is to first record the reverb in mono onto the tracks as you record. This way you can have gated reverb on the drums, perhaps a longish reverb on the vocals and whatever you want on the rest. Then, when you come to mix, choose a short setting on your reverb and add this to all the tracks keeping the output in stereo this time. This has the effect of adding a sense of spaciousness to mono reverbs and is often enough to save the day.

And now on to a few applications:

Method

One thing that betrays an amateur demo is the excessive use of effects, so the one of the first things to learn is restraint. You don't need a long decay time to give drums an expensive, produced sound and 1.2 seconds should be considered a maximum if you're after a fairly typical drum sound. It's always worth experimenting with the different room types if you have access to this facility. This can influence the sound of a drum kit quite considerably, even if you choose the same decay time. As most drum machine sounds are quite recognisable, reverb techniques can often help you to get a much more individual sound. In this case, consider adding a greater proportion of reverb than normal but reduce the decay time to compensate. This same trick is effective on rock guitar and synth sounds, particularly bass ones.

Moving on to vocals, this is another area where it's tempting to overdo things. If you have a reverb unit that allows you to change the level of the initial reflections relative to the rest of the reverb, then try using as high a level as you can set simply to see what happens. It gives the vocals a sparkle that is hard to achieve in any other manner that doesn't clutter the sound with excessive reverb. Units such as the Yamaha SPX90 offer some initial reflection patterns on their own and these are worth trying too. You can always add a little more conventional reverb when you come to mix down. On the new Alesis Midifex, some of the Stereogen programs have this effect and some of the shorter, brighter Midiverb settings perform a similar function. Adding a few tens of milliseconds pre-delay can also help to increase the sense of space added by reverb and it keeps the vocal sound clear by separating it from the following reverb. One instance where long reverb times don't sound out of place is when you are mixing slow flute passages or their synthetic equivalent. Sampled vocal backings can also be made to sound more interesting and less mechanical in this way.

Many digital reverbs give you the opportunity to adjust the pre-delay but a pre-set unit such as the Midiverb also contains pre-delay, though this is of course fixed depending on the setting used.

Traditionally reverb is panned equally to either side, regardless of the position of the original sound, because in real life, reverb is omni-directional. However, there's a case for panning the dry sound to one side and the reverb to the other purely as a special effect. This is particularly effective on short, hard reverb settings incorporating a little predelay. Panning the reverb with an autopanner can also be effective and the chaps at Alesis have not been slow to recognise this as they have built some panned effect into their Midifex.

Specialities

As you may be aware, many specialities may be created using reverb. One such is gated reverb, which was created by feeding the output from a spring or plate reverb through a noise gate which would cut off abruptly once the reverb fell below a set level. This gives a burst of reverb following the sound which suddenly ceases after about a hundred milliseconds, depending on what hold time you set on the gate. Of course this system is totally dependent on the programme dynamics, and quiet passages may not get any reverb at all.

The digital equivalent, often referred to as 'non-linear', is not level-dependent, as it consists simply of a burst of closely spaced reflections following any input. If the input falls in level, you still get the reverb and its level is related to that of the input. This makes setting up easy and the gate length can be set up over a wide range of times, the maximum practical value being just over half a second.

Naturally this effect is very popular on drums but it can be well used on other things too. It's particularly impressive on dirty rock guitar where it gives a raunchy, full sound but without the clutter that conventional reverb would cause. It's also worth trying it on sequenced synth lines as these often benefit from being enlivened. Even vocals can sound satisfactory with a touch of gated reverb, though it's useful to add a touch of conventional reverb too.

And now, backwards

Reverse reverb has been used for over a decade and it used to be accomplished by playing a tape backwards whilst simultaneously adding reverb and recording it onto a spare track. When the tape is again played normally, the reverb appears before the sound rather than after it and builds up slowly with a very abrupt decay. The digital equivalent can't generate the reverb before the event, (as telepathic ICs aren't expected until next year) but they can simulate the reverse envelope. This follows the original sound in the normal way but the modified envelope does give a convincing reverse effect. The Alesis machines give a cleaner reverse sound than most due to their different way of generating the envelope, but virtually all modern digital reverbs offer some variation on this effect.

Unfortunately it's the sort of effect that can be easily over-used, but it can create an interesting atmosphere on vocals. On synths the effect is less easily recognised and so its use may not have to be so limited. The reverse effect gives a breathing quality to sounds and a fairly ordinary synth patch can end up sounding like an exotic sample. If, on the other hand you want a really obvious effect, it's worth trying short percussive sounds such as drums or synth patches having a very fast decay.

Summary

To make good professional recordings that don't appear smothered in effects, it's essential to have some control over the reverberation characteristics of the sound. Nowadays digital reverberation is cheaper and offers more flexibility than ever before, and I'm sure we will see progress in both directions in the future. It is however, imperative to use any effect carefully, and knowing when not to use it can be, if anything, more important than knowing where to use it. When the production is finished, the average listener may well not even realise that any effects have been used but somehow, the mix will sound good to him. Remember that the music comes first and that tastefull application is analogous to using spices in cooking; a little brings out the flavour but a lot drowns it. Now where did I put that Vindaloo paste?