Chronium

Chronium is a sequencer/synthesizer app for creating, recording, and sharing complex melodies simply by a few finger touches.

The main user interface consists of a fingerboard and a control bar. Touch the fingerboard to start, stop, or modify a voice. The horizontal axis of the fingerboard corresponds to different frequencies, similar to a guitar fingerboard. The vertical axis corresponds to different sounds and rhythm patterns which you can configure. When a voice is playing, the corresponding rhythm pattern is shown as a loop around the touch position, along with the red play cursor. On 3D Touch devices (for example iPhone 6S), the pressure applied to the fingerboard affects the sound by changing filter parameters or modulation depths. On other devices, the same parameters are controlled by an estimate of the surface touched by your finger.

The rhythm patterns are produced by thresholding a weighted sum of binary signals. The weights and thresholds can be set using sliders in the pattern editing interface. 7 basic binary signals are available with periodicities ranging from whole notes to sixty-fourth notes. 5 thresholds are used to determine the timing of the notes, the octave, and whether the notes should be accented or not. The weights and thresholds can be set for 3 different locations along the vertical axis of the fingerboard. Patterns in intermediate locations are obtained by interpolating the weights and thresholds. 

Up to 7 different sounds can be placed on the fingerboard and sounds in intermediate locations are obtained by morphing between the two nearest sounds. For this app, an advanced virtual analog sound synthesis engine was developed to enable morphing between classic analog and FM synth sounds.

Chronium can record what you play and share it with other apps as a lossless 32-bit audio file. On devices with an A7 processor or higher (iPhone 5S or higher, iPad Air or higher, iPod Touch 6th Gen or higher), you can also record what you are playing as a video and share it on social media, via email, or to the device's camera roll.

Use Audiobus to connect to other apps. Chronium supports Audiobus state saving so you can load and store your Chronium settings directly from the Audiobus app. Furthermore, Chronium settings can be saved to and annotated in the built-in iOS Notes app and shared via email.