Most of music related tasks need a joint time-because a music signal varies with time. The existing time-frequency analysis approaches show some serious limitations for application in music signal processing. This paper presents an original frequency-dependent time-frequency analysis tool called the Resonator Time-Frequency Image (RTFI). The RTFI is implemented by a first-order complex resonator bank so as to be computation-efficient. Different music analysis tasks may have different time-frequency resolution requirements. Using the RTFI, one can select different time-frequency resolutions, such as uniform analysis, constant-Q analysis, or ear-like analysis by simply setting different parameters; and letting the RTFI generalize all these analyses in one framework. An example of using the RTFI in music onset detection is introduced.