A Thummer is a proposed commercial musical instrument characterized by 1. * at least one isomorphic keyboard, and 2. * thumb-operated and/or motion-sensing expressive controls. The Thummer was to be a type of jammer keyboard. Research suggests that the jammer's combination of thumb-controls and internal motion sensors could give more expressive potential than other polyphonic musical instruments such as the piano, guitar, and accordion. Isomorphic keyboards similar to those used in a jammer have been shown to accelerate the rate at which students grasp otherwise-abstract concepts in music theory.