A.T. Robertson Commentary 1 Corinthians 14:26

"What is it then, brethren? When ye come together, each one hath a psalm, hath a teaching, hath a revelation, hath a tongue, hath an interpretation. Let all things be done unto edifying." — 1 Corinthians 14:26 (ASV)

When ye come together (οταν συνερχησθε). Present middle subjunctive, repetition, whenever ye come together, in contrast with special case (εαν συνελθη, second aorist subjunctive) in verse 23.