Drones are represented as grey buttons. Select a drone to start it. The drone should turn salmon color, and start playing the pitch. If you change tuning or synth settings while the drone is playing, you will need to stop and start the drone to hear the change. If for some reason the drones continue playing when they shouldn't be, hit the panic button on the bottom of the screen.
A tonnetz is structured as a lattice with each node a pitch class (pitches with octave equivalence) and demonstrates the concept of pitch drift visually. In just intonation, the fifth and third will not cooperate to produce the enharmonic equivalence assumed in 12-tone harmony. Therefore, a cello C string will sound quite far from a violin E string, hence the reason for tempering in chamber music. You can find more info in the Xenharmonic wiki.
Travelling horizontally on the tonnetz counts for intervals of a pure fifth/fourth. On the opposite axes, travelling diagonally accounts for the intervals of pure thirds/sixths. Each drone on the tonnetz is a unique pitch class, so enharmonic spellings or the same note name do not refer to the same pitch.
The Circle of Fifths view allows you to control the tempering of your fifths, which allows you to align with meantone tunings useful for early music settings. It is also where you will be able to use 12 tone equal temperament (12TET) which will align with a piano. Selecting a note on the wheel selector allows you to choose the reference pitch from which to tune, depending on the keys you might be using. The app will ensure that the standard A (diapason) remains at the pitch selected and calculates the reference pitch relative to the diapason.
Using the record button (bottom right button) you can create custom drone lists. With a bluetooth page turning pedal (or any hardware keyboard) you can switch between drones in your custom list, allowing for hands-free practicing. Turn on the drone labeled for pedal use, and use your pedal to switch between those drones.
You can save your drone lists as presets with the save button, or start a new one with the New button. Please note that recording a drone will record the pitch it is at, allowing changes in diapason or stop to be included in the custom list.
The first menu at the bottom is the general controls menu. This allows you to select which drone layout you will see - Tonnetz, Circle of Fifths, or Recorded. Use the display mode option to show note names, pitch class integers, or the frequency of the drone. If you prefer a specifc naming system, select the English, Solfège, German, or Dutch system. Diapason refers to the tuning of A4. "Stop" refers to the octave which a drone will play at, with longer stops referring to lower octaves (just like organ stops). Lower stops may not be heard at low volumes.
The synth menu offers basic control over sound generation, with two oscillators. Each oscillator has a knob which will move through the wavetable consisting of a sine, triangle, square, and saw wave. "Morph" indicates the position in the wavetable. You can select the wave icon to move to that position in the wavetable automatically. Control the balance between the two oscillators with the Oscillator balance slider.
Certain effects can be added to the sound. The Sub Oscillator will produce a sine wave an octave or 2 octaves below the drone. The low pass filter limits frequencies to below a certain cutoff, which can be amplified at the cutoff point with the resonance variable. The LFO will affect the filter cutoff, whose variables can be controlled like the main oscillators. The phaser effect can be used to sweep through overtones to create a unique drone sound.
The random menu (indicated by a dice) will allow you to pick a random 12 tone note. This can be used for random scale generation in practice.
The record button is used to record drones to the user custom list. After toggling the button on, it will copy each drone that is started into the custom list which can be used later with a foot pedal.