Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Confusion; Situational Awareness
ATC Issue All Types
Flight Crew Overcame Equipment Problem
Company Policy; Procedure; Human Factors
DFW has an odd system of ground-frequency assignment for the east side of the airport; that has long concerned pilots for the very reason this incident highlighted. Outbounds from the remote; E Terminal spots of XX to YY are often assigned the discrete Ground frequency of 121.80; even though all other east-side operations for the apt are issued 121.65. However; those of us assigned 121.80 are never switched to the 'main' frequency of .65 that everyone else is operating on.On this day; as we taxied out we were assigned 121.80; but the First Officer; to his credit; decided to take the initiative to also pull up 121.65 on the other radio; so we could hear what was being said to and by the other aircraft operating in the same area and taxiways and the same controller. Northbound on Taxiway K approaching Taxiway Z there was a B737 waiting to pull out. Ground issued instructions to them over 121.65 to pull out ahead of us; and then transmitted to us on the same frequency to give way. The only reason we were aware of these transmissions was because we were monitoring both frequencies. We gave way to the B737 without incident and everyone went on their way none the wiser; except us. Had we not been monitoring 121.65 but just on our assigned frequency of 121.80; there's every reason to believe both aircraft would have gotten much closer together before the ground controller might have discovered his error; and ultimately; it was not his error but the assignment of two; discrete frequencies to different aircraft taxiing on the same taxiway.
An Air Carrier pilot reported the crew would not have heard a taxi instruction to give way to another aircraft if they had not been monitoring a different  frequency than the one they were assigned.