Keppy's Synthesizer (Previous name: Keppy's Driver) is a MIDI synthesizer driver, made by the BMT member KaleidonKep99.
Currently the de facto synth of the Black MIDI Team (With exceptions), it has very low latency, while high audio quality.
It runs on the same core .DLLs as it's sister-like synths, CoolSoft VirtualMIDISynth/CoolSoft VirtualMIDISynth 2 and BASSMIDI Driverᴬ.

Download page: Click here

Softpedia page: Click here



  • It's an hybrid between the audio quality from BASSMIDI Driver (no stuttering) and the fluidity from CoolSoft VirtualMIDISynth 2 .
  • There's no click noise when a note is killed.
  • Only one MIDI port, while the user is able to switch between soundfont lists. (Up to 16 lists - 8 are disabled by default)
  • Debug mode available, like CoolSoft VirtualMIDISynth 2.
  • Currently the only one synth that works perfectly with Windows 8.x and newer.
  • No performance impact whatsoever. (When using WASAPI  and ASIO , or DirectSound with the old buffer mode disabled.)
  • Way lesser minimum requirements than BASSMIDI Driver and CoolSoft VirtualMIDISynth.
  • A lot of customization options, if compared to its sister-like synths.
  • MT-32 mode that allows old DOS games or MT-32 specific MIDI to play properly.
  • Temporary voices limit burst if there's enough rendering headroom



Development history

  • Development began in June 20th 2014 as BASSMIDI Driver Mod. It required BASSMIDI Driver to be installed, in order to be used.
  • As of August 15th, 2014, the driver slowly started to become more and more indipendent from BASSMIDI Driver.
  • As of December 28th, 2014, the driver got the ability to use its own registry keys. BASSMIDI Driver is still required for it to work.
  • As of March 1st, 2015, the driver has been renamed to Keppy's MIDI Driver. BASSMIDI Driver wasn't needed anymore.

Data are missing in between March 1st, 2015 and January 23rd, 2016, since KaleidonKep99 removed the source code from GitHub.

  • As of January 23rd, 2016 (version, the driver got reuploaded back on GitHub. It has been renamed to Keppy's Driver. Removed ports I, II, III, IV in favor of a multi-list system with one input port.
  • As of March 7th, 2016 (version, the driver got a feature called "Output to WAV mode" (Now called OTW), allowing the users to output the audio of the driver to a WAV file.
  • As of June 6th, 2016 (version, the driver got the ability to choose the default SoundFonts list to load at startup.
  • As of June 26th, 2016 (version, the driver got a new add-on, the mixer window, useful for reducing the volume or muting specific channels.
  • As of June 30th, 2016 (version, the driver got the ability to enable/disable SoundFonts.
  • As of July 8th, 2016 (version, the driver got a new buffer system, 40-45%~ faster than the old one.
  • As of July 28th, 2016 (version, the driver got the ability to choose the default SoundFonts list to load on a specific program, similar to the update from June 6th, 2016.
  • As of August 12th, 2016 (version, the driver got support for LoudMax, allowing Windows 10 users to enjoy pristine audio without clipping. The next day, the driver got renamed to Keppy's Synthesizer.
  • As of August 18th, 2016 (version, the driver got the "VirtualMIDISynth killer" update to the buffer, making it one the best MIDI drivers for Black MIDI playback.
  • As of September 16th, 2016 (version, Thomas Mundt, the owner of LoudMax, allowed KaleidonKep99 to redistribute the LoudMax libraries in the driver's installer.
  • As of September 21st, 2016 (version, the driver got the Automatic MIDI panic feature (Now called Automatic rendering recovery), allowing it to recover from crash parts faster.
  • As of October 29th, 2016 (version, the driver discontinued support for Windows XP, making it the first MIDI driver to do so.
  • As of December 19th, 2016 (version, the driver got the ability to ignore a specific velocity range, useful when playing Black MIDIs with a lot of note art.
  • As of February 13th, 2017 (version, the driver got the ability to play preview of SoundFonts through the configurator.
  • As of February 28th, 2017 (version, the driver got the ability to mask itself as another MIDI synthesizer/driver.
  • As of March 3rd, 2017 (version, the driver's debug window got a huge UI revamp, allowing users to get advanced information about their computer's specifications.
  • As of July 2nd, 2017 (version, the driver's default audio engine became WASAPI, replacing the aged XAudio2.
  • As of August 20th, 2017 (version, the driver's configurator got the new Telemetry feature, which
  • As of August 31st, 2017 (version, one of the audio engines, XAudio2, has finally been removed. Probably one of the oldest components of the driver, it got replaced by ASIO and WASAPI.
  • As of September 1st, 2017 (version, the driver got the ability to change some critical settings in real-time.
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Special functions

  • People can change between soundfont lists by pressing CTRL and a number from 1 to 8 (CTRL + 1 = List 1 etc.)
  • Able to achieve near 1ms latency by using the ASIO or WASAPI (with exclusive mode enabled) engines.




Soundfont lists page


Keppy's Synthesizer settings


Keppy's Synthesizer advanced settings


Keppy's Synthesizer info page.