There are various theoretical and observational synergies among pulsating A and B stars, because of the similar driving mechanisms and observed pulsation mode frequencies. For example, mode coupling and nonlinearity are predicted in delta Scuti and beta Cephei star, but are not well constrained. We present the results from a thorough search for amplitude modulation in approximately 1000 delta Scuti stars that were continuously observed by the Kepler Space Telescope for 4 yr. Our study demonstrates that diverse pulsational behaviour exists across the classical instability strip on the HR diagram, and we construct models to characterise different physical causes. The upcoming TESS mission will observe a large fraction of the sky and search for transiting exoplanets around bright stars, which will be characterised using asteroseismology. In addition to this, TESS will provide a rich and unique data set of many upper- and pre-main-sequence stars, as Kepler did not observe many of these objects. Therefore, the diverse TESS mission data set will be ideal for investigating the similarities among pulsating A and B stars.