Envelopes

Hello, I am Carlos Devizia from Argentina and our today´s topic is "Envelopes".

As we know, in a synthesizer, sound is generated by the oscillator, then it goes to the filter section and then to the amplifier. This amplifier is designed to change over time and it is modulated by the "envelope", which is basically a path that runs every time a key is pressed. (envelopes can modulate other things on synths, but today we will focus on the envelope as modifier of the amplifier).

The envelope controls how the volume of the amplifier reacts over time.

It has four parameters that are:

A Atack time

D decay time

S Sustain level

R release time

Attack time: every time you hit a key the envelope will run from zero to full value. The more the attack time is increased, the slower it will ramp up. Let's hear what happens with sound if we change the attack. I will play a sound with no attack and then I will gradually increase the attack. (notice that in the case of synthesis, "attack" has a meaning that could be considered opposite to the "attack" meaning if we talk about performing an instrument).

Decay Time: after it reaches full value, the envelope will decay to reach a sustain level. Let´s hear some variations in decay, once again increasing it gradually, I will let the sustain level not too high to make the effect of decay more obvious).

Sustain Level: (notice that this parameter is not related to "time" as the other ones, but is related to "level") It represents the steady state where the note stays while it is being held. Once again, let´s hear an example.

Release time: is the time that the sound needs to reach zero, after the key is released. Let´s hear the effect of "release" in a sound. I will hit a key and release it quickly several times, gradually increasing the release value. The longer this value, the longer it will take to the sound to fade out.

Let´s look at some common envelope shapes and after that, an example of them in a musical context. For this task I will use the excellent freeware synth TAL - Elektro II. I will focus only on the envelope section as this is the focus of this writing, and won´t speak about the other sections of the synth or the parameters involved in the creation of these sounds.

I will speak a little about the characteristics of each type of envelope , and after that I will post an audible example of them.

Switch envelope: It has a fast attack and a fast release, in this case decay does not matter so we´ll put it all the way down and sustain will be at full level. This kind of envelope is great to create sounds that resemble organs, for example. (please, notice that in some synths, an extremely fast attack and release will produce an audible click, this can be solved by increasing a little bit their values).

Sustaining: in this case, the note is sustained and receives energy while the key is pressed. Think about a bowed or a blown instrument, as long as the player moves the arc or blows in the instrument, the instrument will sound.  It has a strong attack, decay and release and the sustain level will be somewhere in the middle. Reducing the decay time will produce a sound with more punch. 

Damped Percussive: this case is the opposite to the sustaining envelope. Think of pressing a piano key, for example, the sound does not sustains and falls to zero, as no energy is added to it. If I release the key while the sound can still be heard, it will be cut abruptly. On the contrary, if I maintain the key pressed the sound will reach zero gradually. In this kind of envelope the sustain goes all the way down, and the duration of the sound is managed by the decay time.

For the following example, I created the sound by pressing the key and releasing it quickly and then pressing the key again and not releasing it letting the sound fall. Please, notice the audible difference.

Percussive: it is similar to the previous one, but in this case the amount of decay is similar to the amount of release. In this way, it won´t matter if I release the key or I don´t, the sound will gradually reach zero (it may change a little bit, but it will be essentially the same).

Quirk: this last type of envelope is unusual. We must have no attack time. We must get the sustain level all the way down, reduce a little the decay time and increase drastically the release time. By doing this, if we play a short note we will obtain a long sound, and if we keep the key pressed we will obtain a short sound, which seems contradictory, but the explanation is that the release time begins right in the moment you release the key.

This last type of envelope, does not have a common use in musical production, but here I made a little phrase using it. When the sound is longer I pressed and released the key quickly, when the sound is short, I pressed the key and stayed there. In my opinion, this type of envelope, could be useful for some random results or experimental performances.

Now, let´s listen to the previous examples in a musical context. This is a rough sketch of a theme I will work on. I added a couple of effects and pan to the sample to make it more musical, but apart from that, all the sounds are from TAL - Elektro II using the envelopes we talked about.

Knowing envelopes will help you create the exact sounds you have in mind. If you want to create an organish sound you´ll probably will use a switch envelope; for a bowed string instrument like a violin or a blown instrument like a saxophone, you´ll use a sustaining envelope; for a piano, a plucked string or a percussion instrument sound you´ll use a percussive or damped percussive envelope. But most important, you´ll be able to create unique sounds that are in your mind. How about a martian cello? or the roar of a space monster? or the chant of a mermaid? If you have it in your mind, knowledge of envelopes will give you the opportunity of doing exactly what you want while creating a sound, not depending on luck but depending on your criteria to do it.

Algorithmic and Convolution Reverb

Hello, I am Carlos Devizia from Argentina, and today I will write about reverb.

Reverb is a very useful effect, which belongs to the category of "Delay Effects".  We can use it to re-create a real space or to create an exotic sonic environment, not necessary inspired in the real world.

Usually, when we record an instrument, we tend to isolate it, to remove reflections in the room and remove as much noise as possible. Though, this is useful at that stage, to record the best signal possible; in the final mix, this kind of sound results unnatural. So, we can use reverb to create the correct space for our production. As we said earlier, we have different approaches to it. We can re-create a natural space, a completely fantastic atmosphere, we can use reverb to separate the instruments in different stages, like if some of them were closer than others, we can define a common space for all the instruments as if they were recorded in the same room and at the same time, etc. We can be completely creative here.

As all the effects in this category, reverb has some basic parameters to care about. The delay time is the amount of time from the input to the output of the signal, the dry/wet control balances the delayed and undelayed signal and feedback determines how much the wet signal is routed back to itself. 

Reverb units are divided in two categories: algorithmic reverbs and convolution reverbs. The first one uses a kind of formula to create the effect. An algorithm is a step by step procedure, a series of rules defined to produce a certain activity to achieve a concrete result. This is the way this kind of reverb works. On the contrary, convolution reverb works based on a recording of a real space that you apply to your sound file.

Both types have their strong and weak points. Convolution reverb is great to re-create real spaces, because you are applying to your sound a record of a reverb made in the real world, however it is limited in the way you can manipulate this. Algorithmic reverb, on the contrary, offers an incredible amount of manipulation possibilities but is does not sound as realistic as convolution reverb.

We´ll take a look at both, we use a couple of plug-ins for our examples, and it is important to say, that though from plug-in to plug-in the names and locations of the controls may vary, the concepts are essentially the same. You may find that some plug-ins have more controls than others, but the main features remain the same. So, no matter with VST you´ll be using, if you understand the main concepts you´ll be able to work with your favourite reverb VST.

Algorithmic reverb

They are usually divided in two separate components: the early reflections which are a series of short delays and the difuse reverb.

In the early reflections section you´ll find a pre-delay control, which works on the beginning on the entire reverb delaying it a little bit. We also can manipulate the space with a control named room space, room shape or a similar name according to your particular plug-in, and that will help us changing the location of the early reflections.

In the difuse reverb section you will control mainly the time parameter. This will affect the size of the room your sound is in. The high end (also high cut, damp, etc.) parameter controls the materials of the room (Some materials reflect the sound better than others, and some are softer than others and this affects the way the sound propagates).

According to the different plug-ins, you may encounter different options and possibilities, like pan controls to panoramize the reflections to the right or to the left, a freezing control to avoid the decay of the reflections, some EQ filters associated to the reverb, to enhance certain reflections on certain frequencies and attenuate some others, etc.

Let´s hear a couple of examples of algorithmic reverb applied to a short fragment of music, in this case played with an alto sax. The first sound shows the dry sound and then the sound processed with different reverb settings. All the examples in this writing do not intend to be musical, they aim to show differents effects achieved by the use of reverb.

Here are some very good freeware reverbs: 

Ambience

Epic Verb

 FreeverbToo

 Mverb

Convolution reverb

In this type of reverb we choose an impulse response, which is a file containing a record of a real reverb that we will apply to our sound. Usually convolution plug-ins have several files associated to them and there are also sets of files on the web downloadable to use with convolution VSTs. The interesting thing about this is that you have an incredible amount of impulse responses available for your use, from very realistic ones to totally strange things. The trick here is to imagine in which space you would like to hear your music and based on that selecting your impulse file. Thus, your music can sound as if it were played in a small room, in a concert hall, in a big cavern, etc. In a convolution plug -in you´ll also find some controls to manipulate the reverb.

Let´s hear a couple of examples of the sound presented earlier in this tutorial with different convolution reverbs applied to it. Let´s listen to the same sound with a couple of convolution reverb applied to it.

Here is a very good Convolution reverb freeware,

SIR

In both algorithmic and convolution reverb you´ll also have the dry/wet control to mix the signal without reverb and the processed signal. The dryer the sound it will sound closer to the listener and the wetter , it will sound far away from the listener.

Conclusion

Reverb is in nearly every element of modern music production, so it has a dramatic impact on the final results we will achieve. Changing the way we apply reverb will change our final sound, so, the more we know reverb and the way it works the more our music will be sounding in the way we want. A good starting point for using reverb is being subtle, unless we are doing something crazy on purpose, subtle adjustments provide great results.