The Well–Sequenced Synthesizer is a series of sequencers that create music in dialog with the user. Through the sequencers’ physical interfaces, users can control music theory-based generative algorithms. This series –a work-in-progress-is composed by three sequencers at this time. The first one, called The Counterpointer, takes a melody input from the user and responds by generating voices based on the rules of eighteenth–century counterpoint. The second one is based on a recent treatise on harmony and counterpoint by music theorist Dmitri Tymoczco: El Ordenador lets users explore a set of features of tonality by constraining randomly generated music according to one or more of them. El Ordenador gives the user less control than The Counterpointer, but more than La Mecánica, the third sequencer in the series. La Mecánica plays back the sequences generated by El Ordenador using a punch-card reading music box mechanism. It makes the digital patterns visible and tactile, and links them back to the physical world.