This lesson, topic, has become extremely controversial today, in more so because sound preachers do not really desire to give complete bible teaching which only comes from sitting before The Lord God daily; rather desire to fill seats instead of making disciples of The Lord Jesus Christ.
However, another reason for the differences of beliefs is because of the increase for demonic examples of it.
In actually studying the word Tongue, came up with 50 times of Strong's G1100.
G1100 means the tone, by implication, a language, specifically one naturally unacquired.