Singing is fine if it relaxes you. What you are really trying to do is silence your inner voice or critic. Being in the accelerated learning state limits the static from the concious mind so that the information can make an impression on your inner mind without any interference. I personally, hum and find photoreading to be an enjoyable process.
You shouldn't really expect to know anything that you photoread unless you activate it. Although, spontaneous activations do occur, they are a bonus.
I have photoread over 60 books on C++ programming and I am finding that my lectures at school are activating the material. It just seems familiar and I grasp the concepts easily. So stick with it.
