Typical propagation diagram of a low-mass subgiant star. The Brunt-Väisälä frequency is represented in blue, delimiting the g-mode cavity (light blue). The Lamb frequency, in orange, delimits the p-mode cavity (light orange). Two g-dominated mixed mode angular frequencies, with n_g = 1, 2, are represented (solid lines in propagation zones, dotted lines in evanescent zones). The G cavity turning points are noted as r_i1, r_i2 and r_o1, r_o2. Finally, the thermal and chemical contributions to the Brunt-Väisälä frequency are represented in green (dashed) and red (dot-dashed), respectively.