Q: What is the difference between open tunings and alternate tunings on a Guitar?
A: With an open tuning, you’re tuning the strings of a guitar to a major or minor chord, so when you strum you hear (instead of EADGBE) an E major (EBEG#BE) or D minor chord (DADFAD), and so forth.
Meanwhile, alternate tunings do not necessarily produce a major or minor chord when the strings are strummed. A good example of this is DADGAD (a Dsus4 chord, which has neither a major nor minor tonality), which is commonly used for Celtic music. A subclass of alternate tunings would include dropped tunings. Dropped D, where the low E string is tuned down to D is a common known example.