Derf,
If you are using a low impedence mic (which is what most pro mics are), you need to use an LXR cable at both ends with a low to high impedence transformer to produce the best sound and at the highest possible volume. If you only use an XLR on one end to a quarter inch jack on the other, you are using a high impedence cable on a mic made for a low impedence cable. The diffrence is in the number of wires used. Although the XLR cable with no impedence transformer will work probably just fine (I do it all the time at my store), you will have more output using a line transformer. These line transformers have a XLR female conector on one end (coming in from the mics XLR male conector) than go through an electronic circuit, usually a small 2 inch module) and then comes out with a 1/4" cable to go into the mic input on the back of the Tyros2.
Again, this is the most effective way to use a low Z mic into a high Z mic input(balanced mic into an unbalanced input), but if you are getting enough gain input into the Tyros you will not harm anything.
George Kaye
Kaye's Music Scene
Reseda, California
(home recouperating from back surgery on Monday)