I personally use
VirtualMidiSynth. I also use synthusr.sf2 font as the secondary font. If you are on Win 8 midimapper has been removed so you can't use the bassmididrv.exe to remap the soundfont. In which case Virtualmidisynth works, works on win xp, vista, 7, also. Under options I turn off Increase process priority to REALTIME, turn on preload soundfont, and under advanced options I set the audio buffer to 250. If you hear crackling, increase the audio buffer.