OB-Xf is an actively maintained, GPL-3.0 virtual analog synthesizer implemented as a JUCE-based audio plugin and standalone application. It emulates the Oberheim OB-X architecture with a polyphonic voice engine, anti-aliased oscillators using BLEP/BLAMP tables, dual filters, ADSR envelopes, LFOs, unison, portamento, and a modulation matrix. The project builds VST3, AU, LV2, CLAP, and standalone targets across Windows, macOS, Linux, and iOS. It also ships a large factory preset library in FXP format, a themeable XML-driven GUI, MIDI learn, MPE support, MTS-ESP microtuning, and Python bindings for offline rendering and patch exploration. The dominant character is a production-grade software instrument, even though it contains a substantial preset asset collection and research-flavored DSP tests.