Notes & Articulation
One of the ideas at the heart of Atrium is that pitch is at the same level of importance as any timbral control. By escaping the strict coupling between pitch selection and envelope articulation of traditional keyboard synths, Atrium offers free interplay between amplitude and harmonicity. Let's explore the different facets of playing Atrium: how to choose pitches, how to voice them, and how Atrium's polyphony interacts with the broad concept of 'notes'.
notes & sustain
First sound! To articulate notes, move the sustain slider up; this slider animates all the active voices at once. As the sustain slider moves up, you'll see the lights to the right come alive and you'll hear the oscillators drone.
Atrium sings with five voices of polyphony. When first powered up, the same pitch is sent to all five voices. Change the position of the notes slider to change the pitch of every voice.
We'll cover how to shape note events in the contour section, and we'll cover how to select which voices are active in the drone section.
chord
While these oscillators sound nice altogether, it's far more fun if the notes are different!
To provide each voice with its own pitch, press and hold chord while moving the notes slider up or down. You'll hear the voices spread away from the root note, either positively (up) or negatively (down). The root note is always the position shown nearest to the notes slider.
The display to the right of notes functions as a small notation device. It represents the active pitches with a piano-style layout turned on its side like a melodica. When chord pushes notes out of range, you'll see them shadowed at half brightness in the nearest octave possible.
chord spreads out all five voices with equal spacing between them — up to a two octave range in either direction. These notes will typically be quantized by scale, meaning if you spread chord a small amount, you'll have multiple voices playing the same pitch.
See below for more details on panning!
As the voices are panned in the stereo field, you'll hear the notes of the chord in opposite channels — for linear scales, these are the highest notes when chord is up and the lowest notes when chord is down. Meanwhile the root note is always in the centre of the stereo field.
If you want to get back to unison, hold clear and press chord.
chord has a larger black key. In Atrium this means the key is a shift or meta key.
octave & glide
In addition to the three-octave range of the notes slider, there are two octave keys. Press either of the octave keys to transpose the current notes by +/- 2 octaves.
Press the glide key to add three depths of glissando between the last note and the next note: just a smidge / acid-style bends / swooping arcs.
Note that glide performs exponential glissandos, moving very rapidly at first, then slowly settling at the target. This is also known as constant time interpolation, ensuring that no matter the distance between notes, they always travel over the same duration.
strum touchplate
There is a touchplate to the right of the sustain slider, which lets us conjure each voice individually. Voices are ordered vertically from bottom-to-top, demarcated by each light trio.
Touch the strum touchplate to articulate the contour (envelope) for each voice.
strum works in conjunction with the sustain slider’s position:
- With the sustain slider down, only the touched voices are sounded.
- With the sustain slider between min and max, touched voices will be raised to full sustain levels, which is a fun way to add ‘accents’ to a drone.
- With the sustain slider at max, touch has no audible effect on already-sustained voices.
All of these are valid interactions: strumming, tapping, holding, or performing little exploratory swipes. Touch the strum touchplate with multiple fingers to articulate many different voices simultaneously.
Moving a touch vertically in either direction picks through the different voices. Meanwhile, where and how you touch on the plate's horizontal axis also influences the results:
Atrium's touchplates use capacitive sensing which allows us to track how strongly any press is held down. In addition, the touchplate itself is designed to have maximum sensitivity in the middle of the horizontal axis, while the edges allow more subtle gesture.
Touch and hold the middle of the voice's zone: This strong and sustaining gesture will open the contour while you hold it. The contour will begin its ramp, with the voice sustaining for as long as its held, then removing touch will release the contour.
Touch and hold the right edge of a voice, then slide it to the centre: Through this gesture you're able to directly control the articulation of the voice from quiet to loud and back again. Using this gesture, you can dynamically play bowed-swells without adjusting the contour settings.
Try different finger positions to adjust the response. A pointed fingertip will be more gentle, while a flat finger will evoke the strongest response. Dragging a flat finger down strum will smoothly fade between different voices.
voicing touchplate
The voicing touchplate, located underneath the piano-overlay, provides additional modifications to the current spread of notes with a note-folding technique. This is best explored with a modest chord spread, to really hear what's going on.
voicing is highly interactive with the active scale selection. Depending on the number of notes in your scale, you'll see drastically different results.
Drag a finger upward on voicing and notice the lighting display indicates the amount of folding. This takes the chord as it's currently voiced and redistributes the notes by selecting a sub-set of possible tones from the scale.
Drag voicing downward, and into the negative region to introduce more bassy tones. This segment of voicing performs "drop-n" voicing tricks, taking one of the voices from a chord and transposing it down an octave. The negative section of voicing steps through five distinct regions, where each voice is dropped one at a time. This technique creates what are often called "sugar chords".
To clear any active voicing modification, hold clear and press anywhere on the voicing touchplate.
Global Tuning
If you're playing with a group, or recording with acoustic instruments that aren't tuned to A440, you can fine-tune Atrium's global tuning:
Hold alt while dragging a finger along the voicing touchplate to set a fine-tune adjustment. Flatten or sharpen by up to 1.2 semitones. More-dramatic tuning changes (and transpositions) are available in the scale editor.
To reset to default tuning, hold alt, then hold clear, then touch voicing.
Panning & strum Voice Allocation
Atrium pans the five voices evenly through the stereo field. Put simply, the root note is always in the centre, and any chord spread is alternatively panned left/right. The result is a pleasing width to the sound without an overt bias of pitch between sides.
If we use the strum touchplate as a form of notation, voices are spread in the stereo field:
R: voice 5 (hard right)
r: voice 4 (centre-right)
c: voice 3 (centre)
l: voice 2 (centre-left)
L: voice 1 (hard left)
In terms of pitch and chord spread, link the strum touches to given notes of a chord:
R: voice 5 (root+4)
r: voice 4 (root+2)
c: voice 3 (root)
l: voice 2 (root+1)
L: voice 1 (root+3)
The above is only precisely true for a specific setting of chord (moved upward by a small amount), but it illustrates the motion of tones. If chord is moved downward, the + above would become -.
In other words, the outer edges will always be the furthest away from the root, whereas the inner edges will be only a degree or two away.