What is the result when everyone in the church service does their own thing at the same time?
The result is confusion. Paul asks what is produced when each person comes together with a psalm, doctrine, tongue, revelation, or interpretation and all do it at once; the answer is confusion. Outsiders hearing a conglomeration of languages would conclude the church is mad or maniacs.
Les explains that when the whole church comes together and everyone has his own psalm, doctrine, tongue, revelation, or interpretation, doing all of that at once only produces confusion. He contrasts that with prophesying, where the Word is spoken forth and an unbeliever or unlearned visitor is convinced and judged, so that the secrets of his heart are made manifest and he worships God. Les also points out that if all speak with various languages, the outsider hearing the conglomeration will say they are mad—the same Greek root as maniac. The correction is that everything be done decently.
How is it then, brethren? when ye come together, every one of you hath a psalm, hath a doctrine, hath a tongue, hath a revelation, hath an interpretation. Let all things be done unto edifying.