QMidiarp Logo QMidiArp - A MIDI Arpeggiator, Step Sequencer and Controller LFO

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LFO Modules

GUI Overview


MIDI Connections
Main Toolbar
MIDI Clock operation
JACK Transport Client Operation
Global Storage
Arpeggiator Modules
LFO Modules
Step Sequencer Modules
MIDI control
Event Log
Example Files
Comand Line Usage and Options
Supported Files

In parallel to the arpeggiators and sequencers, QMidiArp can send MIDI controller data in form of a low frequency oscillator (LFO) to the assigned output. The LFO data consist of controller events that are in sync with the arpeggiator queue. The queue has to be in running state to enable the LFO.
The LFOs are a very versatile addition, since you can either let them run continuously or trigger them by keyboard notes in the same way as all other modules. You can even use them as control sampler/looper, since incoming controller data can be recorded as a waveform and will be played back as soon as the Record button is released. All relevant functions and buttons are themselves MIDI controllable.

Each LFO module has a waveform panel to define the shape of the outgoing data and an output panel to define MIDI Channel, MIDI input port and controller number to be produced. The waveform can currently be set to Sine, Saw Up, Saw Down, Triangle, Square and Custom. The frequency of the LFO can be set in muliples and divisors of the arp tempo, such that frequency of 1 produces one full wave per beat. If frequencies lower than 1 are selected, the length of the wavetable has to be adjusted correspondingly to produce a full wave. The time resolution of the LFO determines the number of events produced every beat and can be adjusted to up to 192 events per beat. Amplitude and offset of the waveform can be adjusted from 0...127. Low resolutions lead to audibly discrete rythmic controller changes whereas higher resolution values lead to more continuous waves.

Muting individual wave points

Individual wave points can be muted/unmuted by clicking on the corresponding location in the wave display with the right mouse button. A muted wave point is shown in darker color.

Custom Waveforms

When Custom is selected, the waveform can be drawn with the left mouse button in the waveform display. A calculated waveform is copied to the custom waveform as soon as it is modified by drawing. This will also overwrite the previous custom waveform with the currently displayed waveform. As all LFO operations, drawing and muting can be done while the queue is running and will have effect on the next output wavecycle.

Play direction and looping

The play mode can be switched between:

  ->_> : Forward and Loop
  <_<- : Backward and Loop
  ->_< : Forward and Bounce
  >_<- : Backward and Bounce
  ->_| : Forward Single shot
  |_<- : Backward Single shot

The direction and loop settings apply immediately when changed on the fly.


The LFO records incoming controller data as selected in the Input panel, when the Record button is pressed. Note that the Record button itself can be attributed to a MIDI toggle controller so that it provides a convenient implementation of a controller motion sampler and looper.

LFO Input panel

The input panel contains settings on which MIDI CC is to be recorded, how the LFO acts to note events received on the input. As the arpeggiators, the LFO can be restarted or (re-) triggered by notes played on the keyboard, and the wave output can be stopped or not when Note Off events are received on the input Channel

LFO Output panel

The LFO output panel contains the port, channel and controller number settings of the LFO data produced by each LFO tab. It also has mute switches for interrupting output.

Example setup for using QMidiArp as a MIDI Controller Looper for live performance:

Controller Looper configuration


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