Sometimes I receive questions that are very easy to ask, but quite lengthy to answer. Here's one…
“What is the best effect unit to use for keyboards live? Example: compressor, enhancer or exciter?”
The answer to this depends on several factors, the first of which is whether you are the player or the engineer.
If you are the player then the answer is simple – use whichever effect makes the best contribution to the overall sound of the band. A secondary priority, but still important, is to make your own individual sound as good as it can be.
For the player, this is a musical question, not a sound engineering question. A musician will choose a keyboard instrument according to whether it sounds good subjectively, and feels good to play. (And doesn't weigh too much!)
There is no engineering criterion that can or should affect the keyboard player's judgment. Does the keyboard sound good in the context of the band? That is all that matters.
And if the keyboard player tries out an effect such as compression and it sounds good for the band, then he or she should use it any way they want.
From the engineer's viewpoint however, things are rather different.
The live sound engineer's role is to make the band sound good for the audience.
The band could play in a small room without a PA system, other than amplification for the singer. If they sound good like that, all the engineer has to do is to get the same sound, but much louder for a larger audience.
If the band doesn't sound good without a PA, then the engineer should seek another band to work with!
So the question here is why should the engineer use any effect at all on the keyboard? If the keyboard player is already getting the sound he or she likes, then the engineer should be content to work with that.
(By the way, in common with normal terminology, I don't class EQ as an effect.)
Let's look at the effects listed in the question…
Firstly compression. Although compression can be used to enhance the sound of a vocal, for keyboards – by which I assume electronic keyboards – the sole purpose would be to control the level.
The thing is that this is better done in other ways. If there is a problem with the level changing even when the player sticks to the same program, then the sensitivity of the keyboard to velocity should be reduced. Many keyboards have such a feature.
By doing this, the difference between quiet and loud would be reduced at source.
If the level changes from program to program, then it would be best to even out the levels in the keyboard, so they all come out at round about the same level.
It would be equally acceptable sound-wise for the engineer to control this at the mixing console, although it does of course give the engineer another thing to think about.
To use a compressor to control level when it is so easily controlled in other ways is simply wrong. The compressor will also change the character of the sound.
The other two effects mentioned are the exciter and enhancer.
The word 'enhancer' can mean many things so it is difficult to comment. But I can say a few words about the exciter.
What an exciter does is add a controlled amount of distortion. It isn't just a distortion box, it is more subtle than that. There are various ways this can be done.
Once again, from the engineer's point of view, we have to ask why?
If the sound that is coming from the keyboard is good, why should it need an exciter? If the reason is that the keyboard doesn't sound good through the PA, then there is something wrong with the PA.
If the sound coming from the keyboard isn't good, then the engineer should discuss this with the player. If the engineer and the player together decide that an exciter is appropriate, then by all means use one.
However, this should not be a decision taken by the engineer alone. It changes the sound of the instrument too much.
So in conclusion, the engineer should not use any effect on the keyboard, without consulting the keyboard player and sharing the decision.
Using an effect won't cure a problem with the sound of the keyboard, nor the sound of the PA.
Now, using effects on live vocals is an entirely different matter…