Predictions of the frequency differences between the reference model and the closest target model, target model #1. The dark blue circles show the actual difference as computed using GYRE. The three other types of points are computed using the oscillation kernels for the variable pairs (N², c), (N², ρ) and (ρ, c). While the (ρ, c) and (N², c) variable pairs agree with each other, the (N², ρ) variable pair shows significant deviations.