Go to my band's RN page (http://www.reverbnation.com/funkundercoverknoxville) and listen to the beginning of Superstition.  What is causing that flange type artifact on the drums (mainly cymbals)  I've noticed it on a few of my other recordings as well.  It's only noticeable if nothing but the drums are playing.  It's not on the wav files and I don't hear it playing through my DAW... it only occurs after I convert to MP3.  
 
That's my BalK BTW :-)

I think you answered your own question.  Try encoding to mp3 at a higher bit-rate.  
Fun band.
Jimmy J

Oh... I honestly didn't know the bit-rate was adjustable!!!  I'll dive into the sub-menus this afternoon.  It IS a fun band.  I cut my teeth on hard rock/heavy metal... I NEVER would have foreseen myself playing this type-of material.  But it's a blast!!!

I didn't know the bit rate was adjustable either, but my drummer uploaded the songs...if anyone cares to listen, reverbnation.com/rumsfeld is my band and yes, that is my singing and bass and I wrote the damn tunes; it's my fault...sob...Tony

Go back to 1/4 tape or cassettes. LOL

Mike ,  
          Bit-rate/bandwidth issues at high frequencies  along with impairment of phase seems to be par for the course  at times with such MP3 issues. Some sites render better then others regarding digital artifacts and anomalies .
 Using the best DA converter on your end might be the best that you can do and if possible as Jimmyj writes opt for highest bit rates when possible.
 
  Terry , Yes __ reel to reel tape !
 Such as my AMPEX AG440C  DC servo capstan 1/2  tape 2 Track Stereo  or 4 track  @30ips with Dolby SR ____Sweet ! Too bad it has a large foot print  and is big and heavy ( more then 24x24) therefore you  can not put it in your pocket, BUT no MP3 can touch it sound wise_____
Here is a similar discussion regarding MP3's ;
 
http://www.gearslutz.com/board/gear-shoot-outs-sound-file-comparisons-audio-tests/613474-can-you-hear-difference-between-these-two-intros.html

Mike,   Musically you guys sound awesome ! Great bass  as well!

I don't have the ears to discern vinyl from CD, but I do notice the degredation with mp3.  But how else can you carry around your entire album collection in your pocket???  The price you pay I guess.  I appreciate the compliment Wolf. I wish we could play-out more, but we're lucky if we gig once a month.

Sonicus..I still have a working Akai 4000DS MkII reel to reel. I recorded a band rehearsal with it a couple of years ago with two mics at the back of the hall and it sounded great.
I love the 'saturated' type sound you can achieve with tape..gives it that prescence which you don't hear with digital these days..or maybe I am looking(or hearing) through rose tinted glasses!!

Terry ,  
             Tape Saturation & other aspects  of  analoque warmth  are discussed in this article.  No intention to hijack this thread but just to add insight,  this might be useful to discuss.
 
http://www.soundonsound.com/sos/feb10/articles/analoguewarmth.htm

I sometimes get that effect if I have layers of the same drums hidden underneath each other on the clips or if the tracks get slightly 'misaligened' by accidently nudging one in the computer.  I use Sonar Producer.

I use Sonar as well.  I haven't had a chance to check on the bit rate thing.  I actually use WaveLab to convert my stereo wav file to MP3.  I'm finally off for a few days, so I'll look into that tomorrow.

I found the bit rate setting on Sonar, but not WaveLab.  I don't think Sonar used to be able to render MP3; therefore, I got used to using WaveLab for that function.  No reason to keep using WaveLab at this point.

No, you have to pay extra to get Sonor to make MP3's. For a $500 program, that seems pretty cheap.