About the mode
The third mode is considered to be the Phrygian mode, and belongs to the harmonic genre.
The second mode uses the harmonic scale:
Listen to the scale.
Master and ending notes
In eirmologika and stiherarika the master notes are Ga, Ke, and Pa. In papadika, the master notes are Ga, Ke, Zo, Ni. The ending notes are in the note Ga.