If you look for the oldest written songs, they’re invariably religious. The evidence used to establish meditation as religiously derived is sufficient to prove the same for song.

In fact, with the evidence at hand, I could just as easily argue that all religion derives from meditation. Secularly speaking, that is a simpler hypothesis than the inverse.

> all modern meditation comes from religious sources

I said modern organised practices of meditation come from religious sources. That caveat is as big as the difference between organised religion and sprituality, generally.