(re: Best MT32 emulator?)
For MT-32 emulation, I think the best is to use the MT-32-enabled version of DosBox 0.6. I’ve never used it myself, so I can’t say anything more.
For your memories of King’s Quest on the PCjr, you are right, it featured bird sounds which version 2 (the common AGI version) didn’t. There is currently no working PCjr emulator, but the Tandy 1000 version of King’s Quest is nearly the same, and works under Tand-Em with sound.