Filter is responsible for timbre change... It does this by removing (filtering) sound energy by frequency. A LPF (low pass filter) allows low frequencies to pass through; those below the "cutoff" frequency pass through, and it blocks high frequencies. By setting the cutoff frequency to 0 you prevent all frequencies above that point from sounding. This, quite naturally, also affects the overall perceived volume. You are allowing very few frequencies out. Amplitude (or loudness) Envelope Generator could be wide open - it matters not, because you are blocking all the frequencies with the Filter.

What you've learned here is the filter's effectiveness and the amplifier's effectiveness are related to each other. This is discussed in detail in an upcoming series in Bad Mister's blog. Envelopes control changes over TIME. The Time (or how long it takes to change) function must be considered when setting up FEG and AEG settings. A closed FILTER (Cutoff = 0) will severely affect overall volume; as you open the filter (move toward 255) the sound will get brighter as you hear more harmonics. You will also hear the timbre get brighter and you perceive this as louder as well. While FEG is related to timbre, changes in timbre also change our perception of loud - loud by frequency.

An EQ (combines filters and amplifiers) affects volume by frequency (and not surprisingly contains filters and amps), boosting bass makes it louder, filtering bass makes it softer, and so on.
In your synth engine: Changing loudness by frequency is the Filter's function, the Amplifier changes loudness of all frequencies together. They are related in this important way.

24dB is how much softer frequencies are an octave *above* the Cutoff Frequency. Say you set the Cutoff Frequency approximately at the "A" below middle "C". Playing the notes between A220 and A440 would result in the volume of A440 would be 24dB down in level from that of A220. That is quite a sharp drop off. Thus CUTOFF FREQUENCY. the harmonics above are "cutoff".

An Attack setting of 77 will allow the FILTER to "open" at a particular speed... by "open" on a LPF is meant you are allowing more sound to be heard. The Cutoff starting at 0 means the filter is completely engaged (all harmonics are being filtered) this is considered "closed"... as it opens you allow more signal out and thus at a speed determined by your ATTACK TIME you begin to hear sound. If you want to begin with sound, start with the CUTOFF FREQUENCY somewhere above 0. The Cutoff Frequency is set by ear... as you increase the CUTOFF value you

From the upcoming tutorial on Synth Basics.....
.....AMPLITUDE means loudness - if, for example, the AMPLITUDE ENVELOPE shuts the sound down, then no matter what FILTER changes you have set, they will not be heard. In other words, TIME is a critical factor. If you setup a FILTER movement (Envelope) that requires more time than the AMPLITUDE envelope allows, well, you simply will not hear it. Make sense? Opening or closing the FILTER when there is no AMPLITUDE to support it, means it takes place but like the tree in the empty forest - no one can hear it!

Thanks for your answer.
But I've tried to set cutoff to 42 and I still get a sound starting from silence.
So I'm waiting for the Guide you are working on form more info.

All sound starts from silence. Ultimately, you shape it from there. KEY ON starts the envelope generators. Before Key On is silence. You can minimize this portion of the envelope by setting the Time related parameters appropriately

Your default Amplitude Envelope Generator setting is what is called an "organ" envelope, because it is a musically immediate Attack, it sustains as long as a key is held, and turns off at KEY OFF. As you said you've done nothing to this (default) Envelope... So your Filter EG should be able to determine the shape of both the timbre which will also influence the overall loudnessof certain frequencies.

I was expecting a sound starting bright and getting dark in about one second.

Setting the Cutoff to 42 is not enough to get what you expected. Try the following ... I'll use a Waveform 1374 _ just the one Element _ and a LPF24d where the sound starts bright and gets dark in about one second:

What you will want to get a feel for is the EG parameters and how they interact.
HOLD - this determines the condition of the envelope at the moment of Key On. You will find both a Time Hold (0-127 the higher the number the longer the Time it will take to move to the next Level setting) and a Level Hold (-127 ~ 0 ~ +127 where negative values close the filter and positive values farther open the filter).
TIME parameters Attack, Decay 1, Decay 2, Release
LEVEL parameters Attack, Decay 1, Decay 2, Release

Use the free Yamaha MOXF6/MOXF8 Editor to better understand how the parameters affect what you hear. The graph is Time x-axis (left-to-right) and Level y-axis (above/below a zero center line). To connect to the Editor you simply need a USB cable (one comes with the MOXF)... program runs on a Mac or PC, and uses the Yamaha Steinberg USB driver for your computer's operating system.

Below you can see the FEG shape ... As you move HOLD (Time) notice how it delays the start of the envelope. If you move the HOLD (Level) it changes the start position as to output from the filter. If you start at -127 it will increase the fade in time. If you start at +127 it minimizes the time to passing signal. Hold can also be used to influence what happens between key strikes.

The Attack parameter for Time is 0, this gives you a musical immediate rise in the envelope to the Attack Level setting +127 ("musically immediate" is when Key On occurs). The Filter is flung open by Key On.

The Decay 1 Time parameter will determine how long the Filter Envelope remains open - in conjunction with the Decay 1 Level which sets the output level _the lower the value the more the filter closes, until at -127 you should hear nothing at all. If you want the filter to initially be open for a second adjust position Decay 1 Level as open and Decay 2 Level for closed.

(Extra Credit: To understand what 0 Level is you must refer to your current Filter Cutoff setting. If you want this 0 Level to be brighter overall, raise the Cutoff setting from 42... the Higher the Cutoff number the more initially bright the overall sound). Watch the graphic to see how this relates to allowing more high frequencies to be heard. Raise the Resonance so you can understand how it places "emphasis" on the actual Cutoff Frequency, by making that frequency louder than all the rest.

The Decay 2 Time is the speed at which it travels to the Decay 2 Level... Seeing it can really help you better understand what you are hearing. A Decay 2 Time setting of 0 will sound abrupt.

Set the FEG as follows:

The five blue boxes can be seen to represent the five Levels: Hold= +0, Attack +127, Decay1 +127, Decay2 +0, Release +0
The angle of the connecting line can be seen to represent the five Time settings: Hold= 0, Attack 0 musically immediate, Decay1 70 or less, Decay2 70, Release 0

Adjust the parameters and listen to the results. The Decay 1 Time set to 70 (and Decay 2 Level of 0) gives you a behavior where the filter closes after about 2 seconds. Settings the Time higher gets exponentially longer, by the time you set to 80 or 90 you are well over 5 and 10 seconds of time (At 127 I'm sure it is in excess of a few minutes). However, increment lower than 70 you will be able to set it to your one second. Somewhere around 50 would be a second... Get a feel for how the Time scale is not linear, by any means.

Time and Level are interactive. The longer the distance between Level settings the more Time it takes to travel there... Set by ear, it is the ultimate judge of what feels right. Notice the (blue) color coding of the Filter EG...

Extra Credit: Behind the blue FEG graphic in red (lighter outline) you can see the AEG superimposed in the background... This is what I was talking about in the previous post... The AEG can be clearly seen... Remember if the AEG is not available to support the Filter movement you will not hear it, but clearly the AEG supports the filter envelope as setup. The PEG (purple) is also shown - it is flat across the x-axis.

Unmentioned thus far, but very important to all of the above is the FEG DEPTH parameter setting... in an initialized Voice this is set to a value of +40, it is responsible for applying the Filter Envelope Generator that we have been working on. With it set at 0 you would not be applying the Filter Envelope and the sound would be virtually in audible - just whatever you are allowing through via the Cutoff Frequency's current setting. Make sense.

If you have not been using the Editor this is as good a reason as any to set it up. It really helps to visualize what you are doing. Let your eyes help your ears (if you will).

Hope that helps.

You couldn't have been clearer. You have a friend in Italy, if you come here I owe you a beer.
Thanks, thanks, thanks,
Luigi.

Excellent, when next I'm in Italy, I'll take you up on that beer! Enjoy!