The Sosnowski Synthesizer
Filter, Filter Envelope, LFO's
The Third Row
.
.
.
The Sosnowski Synthesizer is organized in five "rows" from top to bottom. This section covers the third row, which contains the filter, the filter envelope, and the two low frequency oscillators, LFO 1 and LFO 2. Taken together, these controls work with each other as the most versatile method of shaping the sound from the oscillators. Though satisfying and worthwhile sounds can be made without the use of this entire row, in most cases some or all of its parts will be engaged.
One note to allay confusion: In this
section we detail the "filter envelope". Do not confuse the "filter
envelope" (row three) with the "main envelope" (row four), which will be
discussed on a subsequent page. The "filter envelope" controls only how
the settings of the filter itself are applied to the sound; while the "main
envelope" is a final stage, that shapes the overall sound.
.
.
.
The Filter
.
.
.
The Filter Controls:
At the top left of the filter section is a drop-down menu selector to choose the type of filter (labeled "filter type"). There are five types of filter: Low Pass, High Pass, Band Pass, Band Reject, and Peaking. The different filter types work as follows:
| Low Pass | Lets low frequencies pass while higher frequencies are reduced in amplitude |
| High Pass | Higher frequencies are passed while lower frequencies are reduced in amplitude |
| Band Pass | Frequencies near the cutoff are passed, while higher and lower frequencies further away are reduced in amplitude |
| Band Reject | Attenuates frequencies near the cutoff while allowing those further away to pass at full amplitude |
| Peaking | Amplifies frequencies near the cutoff, while leaving those further away to pass without amplification |
In general, the low pass filter is the most commonly used and the most useful in the
majority of sound requirements.
Below the filter type selector are three knobs labeled "cut-off" (the cut-off frequency setting); "res" (the resonance); and "track" (the tracking). The function of each is as follows:
| cut-off | On low and high pass filters, cutoff sets where the attenuated frequencies begin; on band pass, band reject and peaking filters it is the center of the affected band of frequencies |
| res | Resonance amplifies frequencies in the near range of the cutoff; on low pass, high pass and peaking it effects how much gain is around the cutoff; on a band-reject filter it limits attenuation around the cutoff by narrowing the notch in the frequency response surrounding the cutoff |
| track | Tracking determines whether and how much the cutoff frequency is affected by the pitch value of the note being played: at zero the filter cutoff frequency is not affected by the pitch value of the note played; at higher values the cutoff frequency increases as the pitch of the note played increases; and at maximum, playing one octave higher doubles the cutoff frequency |
In most sounds, the regulation of these three controls, most especially cut-off, merits
careful and considered attention, as they are crucial to the color and response of the
sound.
.
.
>.
The Filter Envelope
.
.
.
.
.
| ADSR Envelope In the Context of the Filter .  . |
|
| attack | The time required for the filter effect to reach full amplitude after the sound is activated |
| decay | The time required for the amplitude of the filter effect to drop to the "sustain" amplitude after the peak "attack" amplitude |
| sustain | The maintained amplitude at which the filter effect remains following the "decay" (this is a level, not a time period) |
| release | The time required for the filter effect to fade to zero when a sound ends |
| amount | The extent to which the filter effect is applied to the underlying sound |
As noted in the header of this section, it's important to remember that the filter
envelope applies to the behavior of the filter, shaping its influence on the
underlying sound across time. This is quite different from, and separate from, the
Main Envelope, which shapes the amplitude envelope of the whole sound.
.
.
.
.
.
.
The two LFO's are identical, but completely independent of each other. When the filter row is active, each LFO can be turned on or off with the button switch in its upper left. When the LFO is engaged, the button glows bright green. When the LFO is off, the button is gray with a minus sign, and the LFO does not influence the filter.
The LFO controls are as follows:
.
.
| waveform | The waveform drop-down menu button selects the wave type the LFO will use: sine, sawtooth, triangle, square, or noise; when noise is selected, note that the speed knob and fast/slow selector are absent since they would not apply |
| fast/slow | The fast/slow button (to the right of the waveform selector) changes the maximum speed of the LFO, with the slow range being very low frequencies, and the fast range engaging a higher range |
| speed | The speed knob sets the frequency of the LFO |
| depth | The depth knob sets the amplitude of the LFO |
| decay | The decay knob sets the time for the amplitude (depth) of the LFO to decay from maximum to zero; clicking the green dot in the center of the knob shuts off the decay and lets the LFO run continuously at full amplitude |
| gain | The gain sets the degree of influence the LFO exerts on the filter behavior |
.
.
.