they can be set to track for keyboard velocity and alter the attack segment of the envelope (enabling a voice to have a soft attack when played softly or vice versa), and note position to alter envelope length (for instance, on a piano sound, having shorter notes higher up the keyboard). Its low-pass filters are analog (CEM 3379), but digitally controlled, and thus can be modulated with a significant number of sources, including LFO, envelopes, velocity, aftertouch, modulation wheel, etc. Even though the filter resonance can be driven to extreme effect, the resonance setting features only 32 steps, and the filters do not fully self-oscillate. The ESQ-1's keybed doesn't feature aftertouch, but the synthesis engine is capable of processing polyphonic aftertouch over MIDI, such as the polyphonic aftertouch implementation of the SQ-80's keyboard. Furthermore, Ensoniq ESQ-1 features amplitude modulation, oscillator sync, monophonic mode, and portamento. Voice programming Each section of the synthesizer is called to screen via a dedicated button, and settings inside each category are made by using one data slider or two +/- buttons. Settings do not influence the sound directly, but rather, changes are heard only when the next note is played. In other words, one can't use the data slider to change the filter cutoff setting as a way of producing a filter sweep, but can use any of the modulation sources to the same effect (including envelopes, the modulation wheel, modulation pedal, or external controllers over MIDI). Any modulation source can be set up to modulate any page of any given program (such as OSC1, DCA1, Filter, etc.). Voices are organized in four banks, and all presets can be overwritten by the user, and exported as banks via the tape-out port in the form of audio-encoded data, thus making it easy to store any number of user-created banks on tape or, for example, a computer. Additionally, it has a cartridge slot for voice cartridges. Commercial cartridges come with two sets of four banks of voices each, but there are also blank or rewritable cartridges. Sequencing ESQ-1 has an eight track sequencer, which can be set to use any of the internal or cartridge sounds, or alternatively set to MIDI output channel for any track separately, while still being able to control a local voice on that track as well. Mixer section provides volume control for local sounds. MIDI output sends program changes, and the sequencer