Question about diads...

HAL9000

https://youtu.be/q0bwQmgS1pY

Jimmie Vaughan’s guitar intro here appears to start with a slide up to double stop consisting only  of F (6 fret on the B string) and D (7 fret on the G string). Ok, in this case I suspect the bass might be playing the G, but even if it wasn’t the guitar would still be recognisably playing a G7. So, how come the brain interprets this a G7 and not, say, a Dm or Bb? 

Brad

Most probably because your ear is used to hearing them in the context of G7, as opposed to the other chords mentioned or different musical situations. 

Without context, these two notes could be many different things. If you’re not used to hearing Ebma9, you’ll struggle to hear them that way. 

Danny1969

Without the G  bass it implies Dm to me , with the G bass it's G7 to me. It's the brain filling in the gap a little after hearing the song in G ..... but if you went and listened to 2 songs in Dm  and then played the D&F your brain decode D minor normally. 

Hootsmon

Diads/intervals/double stops and only becomes a chord when a 3rd note is added....generally