Keys is an instrument with six models: Grand, Upright, Felt, E-Piano, Wurli and Celesta. The pianos come from a string model (inharmonic partials, two strings per note, double decay, hammer, soundboard), so they take a few kilobytes instead of gigabytes of samples and load instantly. The E-Piano barks when you hit it hard, the Wurli has a warm reed and the Celesta has bells made for trap melodies. Tremolo, chorus and reverb are built in, and the sustain pedal works.