Modulus (top) and phase (bottom) of the input impedance of a bass trombone (A. Courtois Legend AC502) with respect to frequency. Blue curve: measured impedance; dashed orange curve: modal fit function with N = 15 modes; green curve: error between measured and fitted impedances, defined by ||Z_fit| − |Z_exp|| and arg(Z_fit) − arg(Z_exp) respectively as regards the module and phase.