Controls

Now lets look at some common controls that are used for programming the reverberations. Like the other effects already seen, the names of the control parameters on the processor can vary from model to model. We will use the most common names.

Always evaluate the decay of the reverb. If you think that the decay seems short, but still gives the correct effect, it is surely better in the overall sound because you don't risk to mix the sounds. As a general rule, never abuse the reverb except in extremely necessary cases (ie: the construction of a particular sound).
In modern sounds the decay of the reverberation is almost always kept short (a general rule that applies to all instruments), especially if the execution time is fast. Note: many times a reverb with a short decay is not always pleasureable, but it surely won't ruin the overall sound.

Correctly adjusting the Pre-Delay, we can postpone the attack of the reverberation. The result is a better definition of the direct sound, free of any phase differences that you would otherwise have if the attack of the effect coincided with the attack of the note. Always remember that the principal sound is made of a note, while the effect always comes later! Another important point is that the Pre-Delay moves the entire reverb effect. Therefore, if you have a Pre-Delay of 50ms for a reverberation that has a Decay of 2 seconds, you will lengthen the reverberation by 50ms. It is therefore worthwhile to shorten the reverb to 50ms, in order to avoid the "over-estimation" of the previously set Decay effect. Unfortunately not all equipment have a Pre-Delay control, and therefore it is better to choose one that is equiped with this control, which is very important for good sound quality.

Equalization. The use of the EQ on the played sound is of fundamental importance, because the addition of the reverb will slightly change the sound. You can therefore intervene, for example, if the reverb is closed with a lot of boom at low frequencies, or if the treble for the reverb is too high. In these controls we generally have the possibility to use some filters that serve to close or cut the passage of certain frequencies. The control of the EQ is usually regulated by two filters.
The High Pass Filter (or HPF) allows frequencies above the set value to pass and suppresses lower frequencies. Normally the control works between the frequencies of 0 and 500Hz. For example, if we set it at 400Hz, the filter will cut all the frequencies below 400Hz, and therefore the reverberation won't be present from 0 to 399Hz, the typical bass frequencies.
The Low Pass Filter (or LPF) operates in the opposite way, allowing frequencies below the set value to pass and closes the passage of the higher frequencies. The control normally works between 4kHz and 20kHz. For example, if we set the LPF to 5kHz, the frequencies above this will be cut and won't be heard, while the frequencies below 5kHz will be present in the reverb.
We can say that the High Pass Filter decreases the bass, while the Low Pass Filter decreases the treble. Usually a crystalline reverberation is preferred for typical acoustic sounds, because when opening the HPF the reverberation is more clean and clear (be careful not to make it too "dry", because it can be irritating), while the darker reverbs are better when playing crunch or distorted sounds. Never muffle the sound. If needed, check the various controls on both the EQ and the effect.

Recommendations for use

The Room-type reverb is frequently used for rhythmics with a decay of about 1-1.5 seconds depending on the particular application of high frequencies. Never lenghthen the decay in distorted sounds because the sound is usually already compressed and long. It's better to use an EQ thats not very clear, seeing it would negatively influence the "dry" sound. We can use the Hall type reverberation only with distorted sounds, using a decay that varies from 1 to 2 seconds, while on the clean solos you can easily lengthen the reverberation delay.