musicN.obj (where n is 0,1,2,3,4 and 5) is file, that contains AKAO frames. AKAO are probably the same as in FF7: AKAO frames.
music0.obj - casual world map Blue Fields music
music1.obj - SeeD music
music2.obj - chocobo music
music3.obj - ride theme (same as train junction music)
music4.obj - action music
music5.obj - ragnarok theme