Each parameter is modulated by its associated oscillator. An oscillator behaves according to its properties (e.g. waveform, amplitude, frequency, pulse width) which it normally obtains from the document, or when View Mix is enabled, from the crossfader mix (see Signal Flow). It's also possible to override an oscillator's properties with alternate values, which the oscillator then obeys regardless of what document is loaded, or what patch is played. Put another way, overriding an oscillator disables its default behavior, allowing you to control the oscillator manually in all situations.
To create or edit oscillator overrides, display the Parameters dialog, and set the edit selection to "Master Offsets". The waveform, amplitude, frequency, and pulse width columns now display the override values for each oscillator. Note that an override is only enabled when its frequency is non-zero; if the frequency is zero, changing the other override properties has no effect. This feature allows you to preset an override, by adjusting its waveform, amplitude, or pulse width, but leaving its frequency zero. The override can then be enabled and disabled live, by controlling the override frequency via MIDI. Oscillator overrides and their MIDI assignments are saved in the playlist.
It's theoretically possible to control all properties of all oscillators via MIDI, but controllers are typically a limited resource. In most cases, you'll want to override selected oscillators, and assign MIDI to their amplitudes and frequencies, or in some cases, only to their frequencies, using preset waveforms and amplitudes. For example, to control Background Hue cycling manually via a single MIDI control, follow these steps: