And from which game did the originate?
There's the:
Kanto Trainer theme (from HGSS), BW Subway Trainer theme, Regular BW Trainer theme, BW Rival theme, DPP Trainer theme Johto Trainer theme (from HGSS) DPP Rival theme Kanto Gym Leader theme (from BW2) BW2 Rival theme XY Trainer theme XY Rival theme
Source Hope this helps.
>There's the Kanto Trainer theme (from HGSS), the BW Subway Trainer theme, the regular BW Trainer theme, the BW Rival theme, the DPP Trainer theme, the Johto Trainer theme (from HGSS), the DPP Rival theme, the Kanto Gym Leader theme (from BW2), the BW2 Rival theme, the XY Trainer theme, and the XY Rival theme. I think that about covers it. Got it from here (lines 5284 - 5329). -Dan-tran, on reddit. (thanks for that)
Source1: http://www.reddit.com/r/stunfisk/comments/21too1/pokemon_showdown_soundtrack/
Source2: https://github.com/Zarel/Pokemon-Showdown-Client/blob/abd86709ea0023c007b98f55e30ed2e5cfc5f70d/js/battle.js