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10.6. Using Reverb and Chorus with Qsynth

While "reverb" (meaning "reverberation") and "chorus" effects are not part of the General MIDI standard, they are offered by most MIDI synthesizers. FluidSynth is no exception, and the Qsynth interface provides a convenient and easy way to adjust settings of the reverb and chorus effect-generators. Experimentation is the only way to know whether you have chosen the right settings, and they will probably change depending on the music you are working on, and even during a piece. Most MIDI sequencers and players (including Qtractor and Rosegarden) allow you to send MIDI messages changing the reverb and chorus settings while a session is playing.
The reverb and chorus effects can be turned off temporarily if you do not plan to use them. To do this in Qsynth, uncheck the "Active" check-box underneath the respective effect generator's settings dials.
The reverb effect generator creates artificial reverberation (like an "echo," but more complex), which occurs naturally in almost all performing environments. The effect generator works by creating a virtual room, and pretending that the user is listening within it. These are the settings offered by Qsynth:
  • Room: Adjusts the size of the virtual room. Settings higher than 100 can cause a situation that escalates in volume to dangerously high levels, even with the lowest possible "level" settings. This is an interesting effect, but caution is advised so that listener do not incur accidental hearing damage. Remember also that the reverb effect can accumulate as time goes on, so it may even take many minutes for the volume level to build to a dangerously high level, depending on the settings.
  • Damp: Adjusts the amount of "sound damping" in the virtual room, affecting not only the time it takes for the sound to die, but the frequencies which are most affected. The greater the damping, the shorter the higher frequencies last.
  • Width: Adjusts the perceived "width" of the stereo image of the virtual room, and also has a large effect on the volume level.
  • Level: Adjusts the volume level of the reverberation.
All of the settings interact in ways that make it difficult to describe any sort of recommended settings. Users are strongly encouraged to experiment with the various settings to find ones that suit their needs. A wide variety of listening environments can be simulated, and the settings required do not always reflect the most logical choice - it is possible to emulate a concert hall with a relatively small "room" setting, for example. Effective use of the reverb effect can greatly enhance the MIDI listening experience.
The chorus effect generator creates the impression that more than one real-world instrument is playing each MIDI line. The effect generator works by slightly responding to each MIDI note several times, with slightly inaccuracies in pitch and time in each response. Although it may seem overly negative to say so, humans intuitively recognize that this inaccuracy is part of real-world, acoustic music, so the chorus effect helps to add a realistic sound to some performances. These are the settings offered by Qsynth:
  • N: Adjusts the number of effect "stages," which allows you to control the approximate number of discrete instruments perceived.
  • Level: Adjusts the volume level of the effect.
  • Speed: Adjusts the speed of the chorus, and so the range of time over which the notes are spread.
  • Depth: Adjusts the perceived "depth" of the stereo image.