Many of the known hadrons are resonances, which are excited states of the same quark combination.
To the student of history there are also interesting resonances with the state of the Frankish kingdom of Jerusalem in those times.
In  we gave a way of handling " negative resonances " by introducing a first order perturbation.
Nearly all of them activate utterly discordant ' sympathetic resonances ' within my awareness; they seem to me altogether too far-fetched!
The deeply grooved surface formed by the highly blazed grating provides a novel route to finding deep cavity resonances with thin structures.