THE ANALOG FOUR MKI/MKII, AND ANALOG KEYS OSCILLATORS
There are several waveforms available to the two oscillators of each synth track. By adjusting the PW parameter, the waveshape can be changed on all types of waveforms, changing their timbre. Furthermore, each oscillator has a dedicated PWM LFO, giving animation to the sound using pulse-width modulation.
SAW
This waveform has a biting, buzzy and distinct sound. It contains all harmonics, both odd and even, of the fundamental frequency. Classic synth basses, strings, and brass sounds are often created using sawtooth waveforms. The PW parameter brings in a second sawtooth, out of phase with the first one. Changing the PW value or engaging PWM varies the phase difference between the two, similar to having two slightly detuned oscillators running. This is useful to get a thicker sawtooth sound with more movement as different harmonics interfere with each other. To get a regular single sawtooth, set PW to mid-position or either extreme value.
TRANSISTOR PULSE
Transistor pulse is special sort of pulse waveform, suitable when you want to achieve acid-like sounds. It sounds a bit more shrill compared to the regular pulse waveform available to the oscillators. PW sets the width of the upper and lower parts of the wave, just like on the regular pulse waveform described below. The major difference is that one part of the transistor pulse waveform is not flat, but rather sloping a bit, thus displaying a slightly similar form as a sawtooth waveform. This introduces more even harmonics, making the sound less hollow. Extreme PW settings, positive or negative, will mute the waveform as the upper or lower part disappears completely. A change in pitch also changes the waveform and pulse-width a bit, giving slightly different sound at different pitches.
PULSE
When the PW parameter is set to its middle value of 0, a square wave will be produced. A square wave contains only odd-numbered harmonics of the fundamental frequency and has a hollow sound, not quite as full as a sawtooth waveform. Changing the PW makes the pulse waveform asymmetric, introducing even harmonics and making the sound thinner and more nasal. Using PWM is the most classic way of adding animation to a synthesizer waveform. When you want to recreate the sounds of old video games, square waves are very handy. Extreme PW settings, positive or negative, will mute the waveform, as the upper or lower part disappears completely.
TRIANGLE
A triangle waveform has a mellow and dampened sound, reminiscent of a mix between a pure sine wave and a square wave. A triangle wave contains only odd-numbered harmonics, but at lower levels than a square wave. A low-pass filtered triangle wave will sound very much like a sine wave. The PW parameter introduces an edge in the waveform, gradually changing it from a pure triangle at mid position to a reversed sawtooth waveform at extreme PW settings.
SUB OSCILLATORS
Each oscillator features a sub oscillator, running at a fixed interval below the oscillator. By activating a sub oscillator, more depth and body will be added to the sound. The sub oscillators work as an extension of the regular oscillator pitch, but will however not be affected by neither waveshaping nor pulse width modulation. Four sub oscillator waveforms exist.
1OCT This option will add a square waveform one octave below the root note. The sub oscillator frequency is 1/2 of the oscillator frequency.
2OCT This option will add a square waveform two octaves below the root note. The sub oscillator frequency is 1/4 of the oscillator frequency.
2PUL This option will add a 25% pulse waveform two octaves below the root note. This selection sounds a bit similar to mixing the 1OCT and 2OCT types.
5TH This option adds a 33% pulse waveform one perfect fifth, which is equivalent to seven semitones, below the oscillator. The sub oscillator thus operates at 2/3 of the oscillator frequency. If for instance, the oscillator plays a G, then the sub oscillator will play the C below it. Together with the other oscillator, this makes it possible to play a simple chord using just one track of the Analog Four MKII.
To get a C minor chord (C, Eb, G), set the oscillator TUN parameter to +7 semitones (for the G), set the sub oscillator to 5TH (for the C), and set the other oscillator to +3 semitones (for the minor third, Eb). To get a C major chord, set the other oscillator to +4 instead (for the major third, E). Suspended chords are created by setting TUN of the other oscillator to +5 (the perfect fourth, F) for a Csus4 chord, or to +2 (the major second, D) for a Csus2 chord. Moreover, four-note chords like the major 7th chord (maj7) and minor 7th chord (m7) are possible by using both oscillators’ sub oscillators in 5TH modes, as these chords consist of two perfect fifths. With oscillator coarse tune settings of +7 and +11 semitones (G and B, respectively) the sub oscillators will be placed at C and E notes, forming a C major 7th (Cmaj7) chord. Tuning the oscillators to +7 and +10 semitones instead (G and Bb) the sub oscillators end up at C and Eb, forming a C minor 7th (Cm7) chord. The desired chord can be heard when the keyboard or the sequencer plays a C note. When playing other notes, the chord will transpose accordingly, enabling simple chord progressions. Transitions between the minor and major variants can be done on step basis in the sequencer by parameter locking the TUN parameter of the other oscillator to +3 or +4 where desired.
OFF This turns off the sub oscillator completely. Note that it is otherwise on, regardless of the regular oscillator waveform setting. The oscillator’s LEV setting then determines the level of the oscillator and sub oscillator combined.
OTHER OSCILLATOR WAVEFORM SELECTIONS
IN L Uses the audio coming from the left external input as the audio source instead of the oscillator waveforms. The incoming audio can then be affected by the AM, the filters, the overdrive and the amplitude envelope of the track.
IN R Equivalent to IN L, but using the right external input.
FDB This setting is only available to OSCILLATOR 1. Instead of using the oscillator waveform as the audio source, the audio coming from the ladder filter output will be used. Just as with the oscillator, the LEV parameter sets the level of this signal path. Turning it up high can introduce a self-oscillating feedback useful for drums or uncontrolled screams. The filter cutoff and resonance settings also affect the feedback behavior. On more moderate levels, it will give a more overloaded sound character to whatever enters the filter from OSC2, similar to the external feedback patch known from certain 1970s synths.
NEI This setting is only available in the OSCILLATOR 2 menu. It will route the audio of the multimode filter output of the track preceding the track being edited. This audio can then be affected by the AM, the filters, the overdrive and the amplitude envelope of the track. In this way track 1 can be sent to track 2, track 2 to track 3, track 3 to track 4. For a completely serial routing, turn down the LVL setting of the routed track completely. This setting does nothing on track 1.
OFF This will turn off the oscillator entirely. The sub oscillator is not affected though.