I find two sets of electrode references in official Muse documents.
In this doc – http://developer.choosemuse.com/research-tools/available-data – you’ll find the electrodes as corresponding to positions TP9, FP1, FP2, TP10, DRL, REF
In this other doc – http://storage.googleapis.com/ix_choosemuse/uploads/dev-site/Technical%20Specifications%2C%20Validation%2C%20and%20Research%20Use%20-%202016%20v6.pdf – you’ll find the electrodes as corresponding to TP9, AF7, AF8, TP10, ref is described as FPz (CMS/DRL)
The second set seems more recent if I trust the mentions made in various messages in this forum. Could it be that this set and corresponding position of electrodes have changed between the first and second versions of the headband?
It wouldn’t change anything for me, but I’m curious to know.