Morphing between scales: from diatonic to dodecaphony

The idea behind the morph

Alea Scale Shifter was made with a particular vision in mind: exploring the relationship between an improvising human player and a machine that randomly shifts from a diatonic scale to complete dodecaphony over time. The morph is where that happens. Everything else in the window feeds it.

The mechanics are simple to state. Every note the app plays is drawn from Scale A or Scale B, and the morph position sets the odds. At 0% every note comes from A. At 100% every note comes from B. At 30%, roughly one note in three comes from B, and you can hear the second scale leaking in before you could name it. The line between the two scales is not a switch, it is a slope, and the slope is playable.

Set up the two ends of the journey

The morph is only as interesting as the two scales it travels between, so build them as a pair with a relationship.

Some pairs that teach you something as they blend:

• A major scale against its parallel minor. The Major ↔ Minor preset does exactly this. The thirds and sixths trade places one note at a time, and somewhere in the middle the line is briefly both.
• A pentatonic against the full scale around it. Five safe notes opening into seven. The Pentatonic Drift preset lives here.
• A scale you know against full dodecaphony. Light up all twelve notes in Scale B and the journey ends in free chromaticism. The Order → Chaos preset takes five diatonic notes and opens them into all twelve over three minutes, which is the vision of the app in one preset.

Each scale also carries its own octave range, velocity range and rest weights, so B does not have to be just different notes. It can be higher, quieter and sparser, and the morph then carries register and dynamics along with the harmony.

Three ways to drive it

By hand. Drag the morph bar while you play. This is the most immediate version of the exercise: you are both the improviser and the weather.

By host automation or MIDI CC. In a DAW the morph position is an ordinary automatable parameter, so the drift can be written into an arrangement, or ride a fader on your controller while your hands stay on the instrument.

On its own, with AUTO-SWEEP. Press it and the machine takes over the journey. Two settings shape the trip:

• Duration, synced to the host in bars or free-running in seconds. Eight bars is a scene change. Twenty minutes is a practice session where the ground moves too slowly to notice until you are somewhere else.
• Mode: One-Shot travels to B and stays. Loop travels to B, jumps back to A and repeats. Bounce goes back and forth, which turns the two scales into a slow tide.

The morph curve decides how the odds accumulate: linear, exponential, S or logarithmic. An exponential curve holds close to A for most of the trip and then falls quickly into B, which is the difference between a drift you can follow and one that ambushes you.

Playing against the drift

The practice value is in what the moving odds do to your ear. Some ways to aim it:

• Follow it. Try to stay inside whatever the machine currently favours. Early on that means playing A material and gradually admitting B notes as they start to win.
• Resist it. Hold your ground in Scale A while the accompaniment leaves without you, and listen to what your held ground turns into as the context changes underneath it.
• Hunt the middle. Park the morph by hand at 40-60% and improvise in the mixture. This region has no proper name in theory, which is precisely what makes it worth practising in.

The timing panel is part of the exercise too. Note rate and note length each choose their own mode - synced, free in seconds, or rolled per note - so the line can be a steady eighth-note stream or something looser that breathes on its own while the harmony drifts.

Repeating a journey you liked

The randomness is replayable: loop a section in your DAW and the app rolls the same dice again, so a pass you liked is a pass you can keep. When a pair of scales earns a return visit, save it - your two scales, with their ranges and rests, store as a .alea file and sit beside the ten factory presets.

Where to take it next

If melody against a drifting scale is one half of the practice, harmony you did not choose is the other. Alea Chord Randomizer, the second instrument in the suite, loops a random progression for you to improvise over - the practice guide covers how to aim it.