There's quite a different issue between typing & creating MIDIs and just playing them. I never had any idea my computer or browser even 'might' play them. I found the 3 programs I mentioned above in a feeeware Usenet group, and have been able to play them just fine ever since.... with many options, like being able to play single tracks of a complex multi-instrument score.
   The ones I noted above are free, and play just fine on my Win7 machine.