Media Player play some Midi Drum files properly, others sound like piano plonking? Why?

I have been looking for a simple Midi Drum audio player so I can scan through my rather massive collection of Midi Drum files, rather than loading every sample into a drum track in Sonar and then deleting it and loading the next till I find the one I like. (It's too tedious.) So I've tried several programs that will load a folder full at one time. Factually, they all do about the same thing and Windows Media Player is as good as any. The problem is that some of my Midi Drum files play perfectly well. They sound like drum tracks. But some just sound like a kid hammering on a piano.
 
I do understand that in a DAW, you would load both into a drum track (channel 10) and they sound like whichever drum machine you've loaded at the time. But there's something different in the two types of Midi Drum Tracks that affect how a Media Player plays them... Perhaps something in the header of the file? Any ideas? Or possibly a free or cheap Midi Drum Audition file that doesn't require loading and deleting one file after another?
 
Thx!

If your drums are literally sounding like a piano, it is probably because the MIDI file is not encoded as general MIDI that includes the instrument to be played by the MIDI stream. It would be possible to just encode a MIDI file without instrument information, load it into a MIDI channel 10 on your sequencer or set it as input to a dedicated drum machine/instrument and have it play normally using the note number to define the instrument. I am pretty sure Windows Media Player would not handle that correctly, since it is expecting general MIDI. It may default to grand piano which is the first instrument in the general MIDI list. 
 
https://en.wikipedia.org/wiki/General_MIDI
 
 

But he's exactly correct about what's causing your problem. I have the same issue...some files properly encoded (with the instrument(s)), some not. No playback app, when given NO instrument info, can guess correctly when it has 128 choices.
 
I just did some testing with Addictive Drums 2. You don't have a sig, so I can't tell what version of SONAR you have, but if you have AD2, you should have the standalone version, as well. You may be able to accomplish what you want just with AD2. [You can click on the "?" and point AD2 to an External MIDI folder, do a Refresh, then set the Library tab on the Beats page to folder you just added. Something like that.]
 
Edit: On further testing, it appears that when AD2 refreshes, it COPIES the MIDI files, retaining your folder structure, into the "Documents | Addictive Drums 2 | External MIDI Files" folder. Good thing MIDI files are small! But it is a way of getting them directly into AD2 for use in SONAR.

johnbarryegan
After a lot of digging around, the issue seems to be that some midi drum tracks are encoded with channel 10, and others aren't, so they default to piano. If you've never programmed, then this is probably pretty complex, but if you have, it'll spell out the format of a midi file:
 

Well.. Can't add an url here. So Google "A tutorial about MIDI specification. Includes examples" and Mobilefish
 

What I would do is open the MIDI files in SONAR and change the channels to channel 10, save as an SMF and they should play correctly in WMP.
But considering the large number of clips you have, that might take a little time.