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guru-sampler

Guru Sampler

Several users have asked if it's possible to import your own samples into Guru Sampler. Yes, it's possible, but the process is NOT simple, and WE DO NOT PROVIDE SUPPORT for it. Click here for more information.

If all you want is a SoundFont player, get SForzando by Plogue Art et Technologie. It's excellent, and FREE for both Mac and Windows.


Guru Sampler is Unify's primary built-in instrument. It's a MIDI-controlled, mono/polyphonic sample playback engine with support for velocity-switching and various kinds of randomized playback.

Guru Sampler's graphical user interface (GUI) window presents all parameters in a single view:

The single view is partitioned into ten distinct sections, which are discussed one by one below.

Master section

The controls in the Master section affect how Guru Sampler responds to MIDI note-events by allocating voices, choosing samples, and setting note pitch:

  • The first pop-up menu selects how voices are allocated in response to MIDI note-on events:
    • Polyphonic: Each MIDI note is allocated its own voice, up to a maximum set by the Voices knob
    • Mono/Retrig: A single voice is used, and the sample and envelopes are re-triggered for each note-on event.
    • Mono/Legato: A single voice is used, and the sample and envelopes are triggered only for the first note in a legato sequence.
  • The second pop-up menu selects whether samples are pitched according to the MIDI note-number:
    • Pitched: the pitch of each sample is adjusted so notes play in tune
    • Unpitched: each sample is played at its original pitch
  • The Voices knob is active only in polyphonic mode. It sets the maximum number of voices which may sound at once, from 1 to 64.
  • The Level knob controls the overall instrument volume.
  • The Shift knob controls how Guru Sampler selects samples for each note:
    • When the knob is in the center (default), the sample-map is obeyed exactly
    • Turning the knob to the right (clockwise) causes progressively lower samples to be chosen for each note, which are then played back faster to bring them up to pitch, resulting in a brighter sound.
    • Turning the knob to the left (counter-clockwise) causes progressively higher samples to be chosen for each note, which are then played back slower to bring them down to pitch, resulting in a darker sound.
  • The Transpose knob applies an integer offset to MIDI note-numbers. The effect is the same as adjusting the transpose setting for the Instrument layer.
  • The Coarse and Fine tuning knobs offset the whole instrument's tuning by semitones (coarse) or cents (fine).
    • As of Unify v1.1.x, the Coarse tuning parameter is hard-wired to MIDI CC#127, for compatibility with MIDIBox
  • The Glide knob (aka Portamento) is only active in mono/legato mode. It sets the rate (in seconds per octave) at which the pitch glides from one note to the next in legato passages.

Amplitude Envelope section

The Attack, Decay, Sustain, and Release knobs control the shape of the “ADSR” amplitude-envelope applied to each note. Note that many samples—especially those recorded from acoustic instruments—already have a natural volume contour, which the ADSR curve modifies. The default shape—zero attack and decay times with 100% sustain—allows the natural volume contour of each sample to be heard without any modification.

The Vel (velocity sensitivity) knob controls the extent to which note volume is affected by MIDI key velocity. At 100%, the response is extremely dynamic; at 0%, all notes play at the same volume regardless of key velocity.

Sample selection controls

The three pop-up menus in the sample selection controls area allow you to select which sample-map Guru Sampler uses:

  • The leftmost menu allows you to select whether Guru Sampler looks at the Samples folder of an available Unify library or in the “global” Samples folder at the top-level of the Unify data folder.
  • The middle menu allows you to select a sub-folder within the selected Samples folder.
  • The rightmost menu selects which sample-map is chosen from the selected sub-folder.

Selecting a library from the leftmost menu automatically selects the first available folder in the second menu. No sample-map will be loaded until a valid item is selected in all three menus.

Just to the right of the rightmost menu are two buttons marked “-” and “+”:

  • The + button selects the next sample-map from the list in the rightmost menu
  • The - button selects the previous sample-map

If the sample name appears in red

If you load a Guru Sampler patch for which the referenced sample-set is not found (e.g., because it has been moved or renamed, or never existed on your disk in the first place), the rightmost menu will change to a button, in which the name of the sample-set is shown in red text.

  • Click the button to pop up an alert box with more information about the problem.
  • When you close the alert box, the control will revert to being a menu, with nothing selected.

Sample Playback direction, Start and Randomize sliders

The two sliders immediately below the row of sample-select menus apply a variable offset from the start of each sample:

  • The Sample Start slider represents the entire length of the sample.
    • If the “thumb” (green dot) is all the way to the left (default), each sample begins playing back at the beginning, so you will hear the natural attack.
    • Moving the thumb to the right causes playback to begin at the corresponding fraction of the length of the sample, thus bypassing part or all of the natural attack.
  • The Randomize slider applies a random offset to the sample-start position:
    • If the “thumb” is all the way to the left (default), the sample-start position will be the same for all notes.
    • Moving the thumb to the right applies increasingly larger random offsets to the start position.
      • In Unify v1.0.12 and earlier, only positive offsets were applied; the sample-start position could never be earlier than that specified by the sample-start slider
      • In Unify v1.1.x and later, the offset is signed, applied symmetrically about the sample-start slider position, and clipped to the sample bounds (e.g. if sample-start is at 10%, but offset is at +/- 50%, any negative offset of more than 10% will push the sample-start to the beginning of the sample).
    • If the thumb is all the way to the right, the sample-start could be chosen anywhere along the entire length of the sample.

To the left of the sample-start slider is a pop-up menu which allows you to select the sample-playback direction: either “Fwd” (forward, the default), or “Rev” (reversed, for creative effects).

Sample map controls

To the right of the sample-start and randomize sliders is a small pop-up menu which allows you to select whether to use the entire sample-map (the default) or select just one sample to map across the entire keyboard range. There are also “+” and “-” buttons to quickly advance to the next (+) or previous (-) item in the list.

Per-voice Filter section

Like a regular synthesizer, each of Guru Sampler's voices features a resonant filter after the sample oscillator, whose cutoff parameter can be modulated by an ADSR envelope which is triggered at the same time as the amplitude envelope, but is separate from it.

  • The left pop-up menu selects the type of filter used:
    • OFF: no filter is applied
    • Lowpass: low-pass filter
    • Highpass: high-pass filter
    • BandPass-1: band-pass filter, type I
    • BandPass-2: band-pass filter, type II
    • Notch: notch (band-reject) filter
  • The right pop-up menu selects the number of cascaded filter stages, which in turn affects the steepness of the filter roll-off:
    • 12 dB: one (two-pole) filter stage, 12 dB/octave roll-off
    • 24 dB: two stages, 24 dB/octave roll-off
    • 36 dB: three stages, 36 dB/octave roll-off
    • 48 dB: four stages, 48 dB/octave roll-off
  • The Cutoff knob adjusts the filter cutoff frequency. As this is a key-tracking filter, the numeric frequency in Hertz displayed while adjusting the knob is for Middle C (MIDI note 60).
  • The Res (resonance) knob sets the filter's resonance in approximate dB
  • The Gain knob controls overall filter gain:
    • Reduce when using very high values of resonance
    • Increase when e.g. high-pass filter output would otherwise be too quiet
  • The Vel (velocity sensitivity) knob adjusts the amount by which the cutoff frequency is adjusted based on MIDI key velocity:
    • In the center position (default), cutoff is unaffected by velocity
    • Turning the knob to the right causes notes which are struck harder (higher velocity) to sound brighter
    • Turning to the left yields the reverse effect: the harder notes are struck, the darker they sound.
  • The Key Trk (key tracking) knob adjusts how faithfully the filter cutoff tracks note pitch:
    • When the knob is all the way to the right, cutoff tracks pitch exactly.
    • When it is all the way to the left, there is no key tracking at all.
    • The default position of 60% yields a good compromise, with higher notes being progressively darker to avoid sounding too strident.

Filter Envelope section

Each voice features an “ADSR” envelope generator to modulate the filter cutoff, which is triggered by MIDI note-on events, simultaneously with the amplitude envelope generator. Note the controls in the Filter Envelope section are only active if the first pop-up menu in the Filter section is NOT set to “OFF”.

  • The Attack, Decay, Sustain, and Release knobs control the shape of the ADSR envelope.
  • The Env Amt (envelope amount) controls the modulation strength. When the knob is all the way to the left, the envelope has no effect at all.
  • The Vel (velocity sensitivity) knob controls the extent to which the modulation strength is affected by MIDI key velocity. At 100%, the response is extremely dynamic; at 0%, key velocity has no effect on cutoff modulation.

Pitch Bend section

The Pitch Bend controls allow you to adjust how the Guru Sampler responds to MIDI pitch bend.

  • The Down and Up knobs control how far (in semitones) the pitch will bend in each direction.
  • The Lag knob applies low-pass filtering to the pitch-bend input, with the result that note pitch lags behind the movement of the MIDI pitch-wheel.
    • When the knob is all the way to the left (default), there is no lag.
    • Moving the knob to the right yields progressively greater lag.

The Down and Up knobs are bidirectional:

  • In the center position (default), the pitch wheel has no effect
  • Turning the knob to the right yields increasingly positive effect.
  • Turning to the left yields increasingly negative effect.

Typically, Down will be set to a negative value (default -2 semitones) and Up to an equal positive value (default +2 semitones), but you can vary these settings for creative effect.

LFO section

Guru Sampler has a single global (not per-voice) low-frequency oscillator which can affect both pitch and filter-cutoff.

  • The left pop-up menu selects among various LFO waveforms:
    • Sine, Triangle, and Square are self-explanatory
    • Saw Up is a sawtooth waveform which starts at 0 and ramps up to 100% on each cycle
    • Saw Dn (down) is a sawtooth which starts at 100% and ramps down to 0 on each cycle
    • S/Hold (sample-and-hold) is a stepwise random waveform created by running white-noise signal through a sample/hold function.
    • Random is a smoothed version of the sample-and-hold waveform.
  • The right pop-up menu selects the LFO waveform polarity:
    • Bi (bidirectional) means the waveform modulates symmetrically above and below zero
    • Uni (uni-directional) means the waveform has only positive excursions; it never goes below zero.
  • The Rate knob sets the LFO frequency
  • The Pitch knob sets the amount by which the LFO modulates pitch
  • The Cutoff knob sets the amount by which the LFO modulates filter cutoff

The Pitch, and Cutoff knobs are bidirectional:

  • In the center position (default), the LFO has no effect
  • Turning the knob to the right yields increasingly positive effect.
  • Turning to the left yields increasingly negative effect.

Mod Wheel section

The controls in the Mod Wheel section affect how Guru Sampler responds to MIDI CC#1 (mod wheel).

  • The Pitch knob adjusts how much the mod wheel affects note pitch
  • The Cutoff knob adjusts how much the mod wheel affects filter cutoff
  • The LFO/Pitch knob adjusts how much the mod wheel affects how strongly the LFO modulates pitch.
  • The LFO/Cutoff knob adjusts how much the mod wheel affects how strongly the LFO modulates filter cutoff.
  • The Lag knob applies a variable amount of low-pass filtering to the mod-wheel input, with the result that the response lags behind the actual position of the MIDI mod-wheel.

The Pitch, Cutoff, LFO/Pitch, and LFO/Cutoff knobs are all bidirectional:

  • In the center position (default), the mod wheel has no effect
  • Turning the knob to the right yields increasingly positive effect.
  • Turning to the left yields increasingly negative effect.

MIDI implementation

  • Note-on and note-off messages are interpreted in the usual way, to trigger notes.
  • Note-on velocity affects amplitude envelope, filter cutoff, and filter envelope amount on a per-note basis, according to the Vel (velocity sensitivity) knobs as described above.
  • Pitch-bend messages are interpreted according to the Pitch Bend controls on a global basis (all notes affected), as described above.
  • MIDI CC#1 (Mod-wheel) messages are also applied on a global basis, and can affect note pitch, filter cutoff, pitch LFO amount, and filter-cutoff LFO amount according to the Mod Wheel controls.
  • MIDI CC#64 (Sustain-pedal) messages are interpreted in the usual way, to hold and release sounding notes. CC values 0-63 are interpreted as “pedal up”, values 64-127 as “pedal down”.
  • As of Unify v1.1.x, MIDI CC#127 is hard-wired to the Coarse tuning knob (see Master controls above). Guru Sampler subtracts 64 from the unsigned CC value (range 0-127) to obtain a signed value (range -64 to +63) to set the coarse-tuning adjustment in semitones.
guru-sampler.txt · Last modified: 2020/08/15 00:49 by shane