As I posted, DOSBox does not emulate Yamaha or Casio, so there is no setting to change that. You would have to code that emulation. The DOSBox devs have never done so and will probably never do so since so few games supported them, especially when SCI0 was the current Sierra interpreter.
DOSBox can emulate PC speaker, AdLib, the various SoundBlaster models, GameBlaster, Gravis Ultrasound, Disney Sound Source (Covox Voice Master and Speech Thing compatible), Tandy and MPU-401. There are special builds of DOSBox that have Munt built in for Roland MT-32 sound.
You need do nothing for SB sound except select AdLib in the RESOURCE.CFG and have added the AdLib track in Soundbox for you SOUND resource.