The phrase "tying in" is often used to describe the process of connecting two or more things or ideas together. Antonyms for this term could include "separating", "disconnecting", or "untangling". If you are looking to undo or break apart a connection, you may use antonyms such as "disengaging", "disassociating", or "disuniting". Similarly, antonyms like "uncoupling", "dividing", and "unrelated" could also be used to describe the opposite of "tying in". It is important to note that antonyms may vary depending on the context in which they are used, so it is always advisable to use a word that accurately reflects your intended meaning.