What do we do with the U-shaped tuning fork pillars?

Solution 1:

The left and right motors in your controller will play a pattern when approaching these. It will pause briefly before repeating. You need to mime the pattern back with your left and right triggers.

My vibration was off, so I missed this the first time through. If you're having trouble, the right motor was a higher pitch in my case. Instead of feeling the sides, I listened for the pitch.

As far as I know, across ports, you can't solve this on your own without a vibrating controller.

Here are the codes, if you're lazy or without:

• Waterfall neon pink/blue subroom tuning fork: LT RT RT RT LT RT RT LT
• Lighthouse tuning fork: LT RT RT LT LT LT RT RT RT RT
• Sewer tuning fork: LT LT LT RT LT RT LT RT
• Lava tuning fork: LT LT RT LT LT RT RT RT

Solution 2:

If you're playing on the PC, while you're standing near the tuning fork a low tune will be will be played on the left or right earphone. Press the corresponding key (A or D) to rotate the perspective following the tune.

I checked with my headphones it's very subtle but it's there. So, I think with normal speakers you'll definitely not hear a thing ;-)

Source : http://uk.ign.com/wikis/fez/Tuning_Fork_Rooms