This might be of interest to the genuinely curious.
https://www.youtube.com/watch?v=VnwGj3tm_zc
Glossolalia never includes sounds not within the speaker's own language. English speakers, for example, have a wide range of sounds to put together in unusual ways, but they don't use sounds that the English language doesn't require.
Linguists (people who make a point of understanding how language works) have innumerable recorded examples of glossolalia to study, yet none of them (that's none as in zero) show any kind of pattern or repeated words or sequences of sounds as every real language has. Some simple sounds repeat, as in 'nanana' or 'mamama' that you might hear when someone is speaking in tongues, but those little staccato-ish noises only sound like foreign language to people who don't know better.
Babbling nonsense is something every human brain is born with the capacity to do, and barring some defect or problem, every human babbles nonsense as a baby. But every baby also soon learns two things about language: that sounds have meaning and that babbling nonsense is not socially acceptable after toddlerhood. The cognitive mechanisms of instinctive baby babbling is probably the same mechanism behind glossolalia, and it's a mechanism that doesn't need conscious intent to happen; it just needs the right brain state and social conditions to temporarily override the early programmed inhibition against babbling.
There's much more to this that is fascinating and quite revealing, and probably a bit embarrassing to people who once thought speaking in tongues is supernatural, but again, to the genuinely curious, there's plenty of literature and commentary from linguists, neuroscientists, and other experts on this topic available.