Qsynth is a fluidsynth GUI front-end application written in C++ around the Qt4 toolkit using Qt Designer. Eventually it may evolve into a softsynth management application allowing the user to control and manage a variety of command line softsynth but for the moment it wraps the excellent FluidSynth. FluidSynth is a command line software synthesiser based on the Soundfont specification.
Qsynth is free, open-source software, distributed under the terms of the GNU General Public License (GPL) version 2 or later.
Sourceforge project page: http://sourceforge.net/projects/qsynth