In some implementations, a computing device can be configured to present a graphical user interface that enables the dynamic authoring of music by a user of the computing device. The computing device can present a grid of cells, where each cell represents a music segment. The cells can be configured to playback the music segment once or playback the music segment in a repeating loop. The user can select (e.g., touch) one or more cells in the grid to cause the corresponding music segment to play. While playing selected cells, the user can provide input selecting various musical effects to apply to the playing music. The user can record a dynamically selected sequence of cells and musical effects to create an original musical product.