X4 by Ketron was released in the early 2000s along with the rest of the X series. Compared to X1, the device was offered to users at a reduced price, as it lacked a keyboard, modulation wheels, speakers, but had a more elaborate central panel.
Anyway, X4 has the same features as its "brother": a fairly extensive control set, a graphic TFC-display with backlight and dimensions 240x128. On the screen you can observe the main information (name, instrument, faders, etc.)
X4 has a wide range of sounds: PCM-samples, 276 sounds, 20 drum kits, 231 percussions, drum grooves, analog waves (sawtooth, square, sine). Moreover, the synthesizer has 128 programmable user voices with envelope control, LFO, wheels, aftertouch and effects. X4 also has 198 kinds of auto accompaniment and 198 custom styles with programmable parameter settings.
The synthesizer boasts a variety of effects, ranging from reverb/delay and ending with a distortion/wah-wah option. The sampler allows you to store up to 8 MB of 16 bit/44.100 kHz data. There you can edit the time, loop type, reverse and delete. The rear panel of X4 features inputs for stereo headphones, 2 line inputs, a microphone input, MIDI input/output/thru, 2 outputs, and connectors for sustain and volume pedals.