Bard's Leap Summit is a wooden plank at the very top of
Lost Valley Redoubt.
After fighting your way through a group of Forsworn to get to the top of the ruins, you will see a walkway extending over the edge of a waterfall. If you jump off the walkway into the pool below and survive, a ghost named
Azzadal will appear. He will tell you that he attempted the jump as well, but that he obviously failed to survive it. He will then play you a song that will increase your speech skill by one point.
Note: I did this successfully with the help of using my "Whirlwind Sprint" shout right before I got to the end of the plank and jumping into the water below. Also, the person who posted this on UESP.net said you only get one speech point, but this may vary, as my speech increased by 2 points from 48 to 50.