We interpret our previously published results obtained using a technique called current-imaging tunneling spectroscopy (CITS) to study the detailed electronic structure of the CuO chains in the high-temperature superconductor YBa2Cu3O7-x near the Fermi level. Our CITS data comprise sequences of 32 simultaneously obtained images taken at bias voltages ranging from -78 to 72 mV. Cross sections of the CITS data, normalized-conductance analysis, and logarithmic-derivative analysis allow us to examine in detail the behavior of electronic modulations along the CuO chains and the energy gap in the CuO chains of YBa2Cu3O7-x. This new analysis lends a strong foundation to our previous interpretation of the CITS data [H. L. Edwards et al., Phys. Rev. Lett. 75, 1387 (1995)].