Headphones are a must if you want to get the full effect of the head-cleaners hypnosis tapes. This is because there is a somewhat different presentation in the left versus the right channel of each stereo, dual voice recording.

Decent headphones are strongly recommended -- costing more than $10 US. The very cheap headphones -- especially those that come free with inexpensive tape players -- seem to make some of the low tones of my voice sound more like loudly snapping plastic spoons.