A method of operating a UI for controlling a virtual musical instrument implemented can include receiving an input corresponding to a selection of a cell within a particular array of cells arranged in a sequential arrangement within a cell matrix, each array of the cell matrix assigned to MIDI notes associated with audio sample data stored in a computer-readable medium that, when triggered, causes the audio sample data to output corresponding audio, and each cell within its particular array of the cell matrix, in response to being selected for playback and upon being triggered to begin playback, causes the audio sample data corresponding to the cell's particular array to be played. The method further includes determining that the input's duration is above a threshold time and expanding a size of an array containing the selected cell and adjusting the adjustable parameter of the selected cell based on the input.