We present a new Dynamic Tonality MIDI sequencer, Hex, that aims to make sequencing music in and across a large variety of novel tunings as straightforward as sequencing in twelve-tone equal temperament. It replaces the piano roll used in conventional MIDI sequencers with a two-dimensional lattice roll in order to enable the intuitive visualization and dynamic manipulation of tuning. In conventional piano roll sequencers, a piano keyboard is displayed on the left side of the window, and white and black note lanes extend horizontally to the right, into which a user can draw a sequence of notes. Similarly, in Hex, a button lattice is displayed in its own pane on the left side of the window, and horizontal lines are drawn from the center of each note to the right. These lines function as generalized note lanes, just like in piano roll sequencers, but with the added benefit that each note lane's height is always proportional to its pitch, even if the user changes the tuning. The presence of the button lattice on the left side of the window illustrates exactly which buttons a performer would play in order to replicate the sequence when playing a physical button lattice instrument.