When I used to attend Pentecostal services with my first wife's family (no, I wasn't one of them but attended out of love for my wife and her family because it was REALLY important to them that I go), I always noticed that the tasks of speaking in tongues and providing the "interpretation" were separate tasks carried out by two or more people. Even then, I thought, "What a nice hustle. Everyone can play and no one is really responsible for being right or even honest."
I've long thought it would be interesting to conduct an experiment using several different Pentecostal churches. Plant some people in the various churches; have them attend long enough (and seemingly enthusiastically enough) that they become trusted members of their respective parishes. Then in each church have the plants "speak in tongues" -- each repeating the same carefully rehearsed nonsense to phonetic perfection -- and record the "spirit-guided" interpretations to see how widely they diverged. Then share the results with the pastors and congregations to watch them go into panicked, righteous-fury damage control.
I've long thought it would be interesting to conduct an experiment using several different Pentecostal churches. Plant some people in the various churches; have them attend long enough (and seemingly enthusiastically enough) that they become trusted members of their respective parishes. Then in each church have the plants "speak in tongues" -- each repeating the same carefully rehearsed nonsense to phonetic perfection -- and record the "spirit-guided" interpretations to see how widely they diverged. Then share the results with the pastors and congregations to watch them go into panicked, righteous-fury damage control.