A microelectromechanical resonator may include one or more resonator masses that oscillates in a bulk mode and that includes a first plurality of regions each having a density, and a second plurality of regions each having a density, the density of each of the second plurality of regions differing from the density of each of the first plurality of regions. The second plurality of regions may be disposed in a non-uniform arrangement. The oscillation may include a first state in which the resonator mass is contracted, at least in part, in a first and/or a second direction, and expanded, at least in part, in a third and/or a fourth direction, the second direction being opposite the first direction, the fourth direction being opposite the third direction.