Dave –
No mistake at all.
Although I do have a sense of aesthetic romance and accept we do use the word "sing" and its relations loosely, whale calls would hardly be thought of as "song" if made in the open air. It would be simply the whale's "call" and a lot of it would sound pretty harsh to our ears. It would be more farm-yard than dawn-chorus.
We call it a "song" only because it sounds to us as if singing; but the effect is not produced by the animal. My objection is less to the loose use of the word "song" than to the assumption based on ignorance that credits the whale entirely.
The plangency that has what our Mam would have called "soppy dates" going all romantic and giving birth in paddling-pools, is due solely to the ocean being highly reverberant between its surface and density boundaries below. These are part of its acoustic properties that also allow whales to hear each other over considerable distances; but let's not credit the animals with being some sort of sub-aquatic opera stars. They just wild animals doing what wild animals do – announcing territories, foraging for food and finding herds or mates.
'
And toads? I have a frog colony in my garden, and can assure you that though I like hearing their bubbling little croaks, a "song" it is not!
'
Once had a guinea-pig. They make all sorts of little chirps and squeaks, and the nearest human-made comparison I can think of, is not Gotterdammerung but an injector with a tiny air-leak!