As I visualize this, I see a big mess being made.
A pressure washer?
Remove the brick and immerse in gasoline?
Paint the brick?
Install a phony ledge as a cover up?
A high pressure steam cleaner?
It could be worse as the tar shrinks and cracks leading to water leaks. Had new tar been applied every three years as maintenance, imagine the ugly build up !
Probably th only thing practical if wire brushing the dried and caked tar..
What a problem, the cure could be worse than the symptom..

Hi

We have a similar issue on our 1910 brick home where the old mudroom was attached to the back of the house. We've rebuilt the mudroom and the new flashing mostly hides the old tar, but where you can see it on the old roofline we've had to try and chip it off with a chisel. You have to be careful because it actually takes pieces of the brick with it, but it does get it off.

We've decided to leave most of it as we have paint on our bricks and sandstone on other parts of the house which we're planning on having CO2'd off sometime in the next few years. Sandblasting is too harsh on old brick.

If your brick is now inside (ours is outside) you can still go with a blasting-type removal (can't remember the name of it but it is for interior use), but it's probably better to chip as much as you can and then try to hide it in some way as suggested above - a shelf or wreath, maybe some decorative wood trim. Other than that, paint is your next solution. Oh, and just so you know, you can't get it out of the mortar without digging into it and ruining it (which is why we're now waiting to blast it off with the rest of brick paint and repoint).

You might want to try asking the Old House forum as well.