At some point in the history of the believers in the Corinth, they (some of them anyway) apparently wrote a letter to Paul. He had traveled to Corinth (a major city east of Athens) earlier and had spent almost two years proclaiming the gospel and strengthening those who received the message.
Eventually, after Paul left on his continuing journey, some troubles and questions arose among the Corinthian believers. In response to their questions, Paul wrote a letter back to them. One of the questions that Paul answered concerned spiritual gifts (1 Corinthians 12-14).
He begins by reminding the Corinthians that only God could give them gifts, and he did so according to his own grace and desires. All spiritual gifts (and, thus, all believers) are necessary and important – especially those that may seem less important. (1 Corinthians 12)
Next, Paul tells the Corinthians that any spiritual gift (even the greatest) was worthless if the person did not love others. He said that eventually all spiritual gifts would cease (would no longer be necessary), but love would never cease. (1 Corinthians 13)
Within these two sections, Paul lists several different types and forms of spiritual gifts, all of them given by God for the benefit of others. While he says that different people are given different gifts for different reasons, he does not actually differentiate among the gifts (i.e., he does not call some “sign gifts” or “miraculous” gifts). To Paul, all of the gifts of the Spirit are “miraculous” because they are given from God through people.
In the last part of his answer to their question about spiritual gifts (1 Corinthians 14), Paul focuses on two of the spiritual gifts that he had already mentioned: prophecy and tongues. To Paul, there is one major difference between these two gifts: prophecy is directly understandable by people while tongues must be interpreted otherwise it is not understandable. In fact, Paul gives several examples, illustrations, and exhortations that prophecy is more beneficial when the church is gathered together specifically because people can understand it.
If we understand this major point in Paul’s argument, we can see that Paul is not only talking about prophecy and speaking in tongues. He’s using prophecy as an example of something that is understandable to all, and he’s using tongues as an example of something that is not directly understandable. (Of course, if the tongues is interpreted, then it becomes understandable.)
In this way, we can see that the end of Paul’s instructions (1 Corinthians 14:26-40) can help us understand other types of speaking and/or serving when the church is gathered together. Is the activity/speaking directly understandable to those gathered? If so, then it would fall under the guidelines that Paul gives for prophecy. If the activity/speaking is not directly understandable, then it would fall under the guidelines that Paul gives for speaking in tongues.
Teaching, praying, singing, etc. (if done in a way that others can understand) should be by two or three (one at a time) then the other would judge/discern what was said/sung/etc. If these things are done in a way that others can’t understand, then they should only be done by two or three (one at a time) if someone can interpret. (Of course, the interpretation would then follow the guidelines for prophecy, including being judged/discerned.)
It’s clear from the entire passage (1 Corinthians 12-14), that Paul is not ONLY concerned about prophecy and tongues. If we carry this broad concern into 1 Corinthians 14, then we can see that Paul’s guidelines are not only for prophecy and tongues.