Ableton Live 9 displays the MIDI note of each of the pads on the Drum Rack in the status bar when hovering the mouse over it. For the Kit-Core 808 Drum Rack instrument for example, the ‘Kick 808’ maps to the C1 note, the ‘Clap 808’ to D#1 note.
I mapped the pads (bank A/B) of my Akai MPK Mk2 mini MIDI controller to the midi notes shows in the Ableton Drum Rack.
For some reason when pressing the pads, they were off by 1 octave. Triggering pads that were not visible and had no sounds loaded on them.
Drag the ‘+ 12.adv’ MIDI Effect from the ‘Pitch’ category onto the section just in front of the Drum Rack, so it will transpose the incoming midi notes by +1 octave (12 semitones).