Is there a way to change an object's object type or add a subcategory to an object type?

[Erich Gercke]

We have a large inventory of microphones, all under an object type of Microphones.  We now need to separate our microphone inventory into two sub-categories, "USB Microphones" and "Recording Microphones".  Is there a way to either change an object's "object type" or to add sub-categories to an existing object type that existing items can be sorted into?