Quite a good article this is on Music synchronizes brainwaves across listeners. Music creates engagement between people. People exposed to music (especially live music) can cause much inter-subject correlation of various neural responses. Also consider this article on Interactions in the classroom which studies group interactions and brain synchrony.
Inter brain synchrony (IBS) has been observed in many social interactions. IBS has been observed between people in: heart beat, music performance and listening, brain waves, video gamers, movie watching, duetting pianists, team collaboration, team work with two aircraft pilots, child-mother relationship and other activities people do together. In most cases researches have observed the IBS behavior by using fMRI or EEG.
Inter-Brain Synchronization during Social Interaction https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2923151/
The Brains of people playing online video games synchronize, even when there is a physical distance between the players. https://neurosciencenews.com/brain-sync-distance-21330/.
Today people are developing technology to interface directly with the brain. One of the more safe ones (besides just a keyboard and mouse) is EEG (ElectroEncephaloGram). With EEG electrical probes are attached to the head on the surface. These connections are wired to a pre-amplifier or instrument amplifier, digitized and feed into a PC or Mac computer for analysis.
Several very low frequency brain waves have been discovered. The waves are actually radio waves (electro-magnetic) but the magnetic component is so small that just the electrical component is picked up.
Here is a few great articles:
Brain Computer Interfaces
Interface Tech for the Brain
Great article on the current research state of mapping the human brain.
New technique to examine how the brain categorizes images.