3'

Mastering the three draw half step bend (3') and it's quartertone higher brother (same, but slightly less bent... between 3 and 3') in second position is imparetive to being a good blues harmonica player.

Most players will play bluesy notes (1', 2", 4', 5, etc.) and neglect to bend the 3 slightly, resulting in a very awkward sounding... a mismatch of intensions. This is one of the defining elements of a player's skill level. The ear to recognize that this doesn't sound good and the skill to change it.

If you're playing light, major and happy... don't bend that 3. The 3 draw is a beautifully major note (think Major Pentatonic Scale).

If you're playing jump and swing blues and slightly bluesy phrases, bend that 3 down a quartertone (most common... 80% of the time?).

If you're playing bluesy-blues, dark or minor... bend that three down exactly to the 3' (think Blues Scale).