Wet Bass - amSynth :: Envelope Filter

However, in certain cases, you may want to use the filter envelope to remove all frequencies. In this case you would use the manual filter control to close the filter completely, and then set the envelope to open it and return it to the closed position at the end of the Release phase of the envelope. Remember to make sure the the release on the volume envelope goes on long enough to let you hear the effect of the filter envelope. It is also best if you set the volume attack to minimum and the volume sustain to maximum. In general, you should use the manual filter cutoff to set the start and end position of the filter. Remember that if the manual filter cutoff is set to fully open the filter, there is no way the envelope can affect the filter any further (unless you have one of the more flexible synths which allow for negative settings of the filter envelope). So make sure that the filter is at least partially closed before you start trying to hear the effect of the filter envelope. You will also need to set the amount of effect that the filter envelope has on the cutoff position (look for the parameter on your synth labelled Filter Env Amount, or perhaps just Filter Amount). If this is set to zero, you might spend all day adjusting the filter envelope parameters without hearing any difference! The Filter Amount control determines how much movement the envelope will induce in the cutoff frequency. If you set a large amount, the filter will probably be fully open at the end of the Attack phase of the envelope, and lesser amounts will cause it to open up less.

To imitate the natural harmonic decay heard in 'plucked' acoustic sounds, you should set the attack of the filter envelope to zero, so that when you play a note, the filter will open up fully straight away. If you use a slower attack, the note will sound more like a instrument being bowed or blown softly to start with and then increasingly harder. Again, these are just examples from the acoustic world to help you understand what you are doing, not attempts to make exact copies of 'real' sounds. The great thing about analogue synthesis is that you can create lots of sounds which don't exist naturally, and if you have access to more comprehensive analogue synths, you should also experiment with envelope control of band-pass and/or high-pass filtering. Similarly, if it is possible to set a negative envelope amount to the filter on your synth, check out the effect that this gives. In this case, you should set the manual cutoff to the most open position that you want it to be, as the negative envelope will close the filter to start with, and then return it to the most open position at the end of its cycle.

It is always a good idea when experimenting like this to work with fairly long attack, decay and release times, with the sustain level at about half way. This gives the untrained ear more time to follow what is happening to the sound during each phase of the envelope. When you feel comfortable with the slow movements, reduce the times so that the cycle happens more quickly. Once you have heard a filter opening slowly and then sped it up bit by bit, you will soon recognize the characteristic sweep, however fast it is happening in a sound -- if you have trouble, you can always turn up the resonance, which will help pick out the filter movements.

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