I'm snugly wrapped in a dry flotation cocoon, aromatherapy scents filling the air. Yet, despite the dream-like atmosphere, I'm becoming increasingly tense and tetchy. The problem isn't the spa, or the treatment, which is wonderful. What's getting me in a lather - and rapidly defeating the object of the exercise - is the music: a floaty, synthesised track on a repetitive loop. I'm not alone in my aversion to spa music; a quick straw poll among friends reveals many who share my dislike for the customary massage-bed muzak.
Cathy Winston, 34, is one of them. "I loathe pan pipes, and I'm not keen on whales or gongs", she says, "As for trickling waterfalls, they just make me want the loo part way through the massage." If so many of us object to the sounds piped in during our treatments, why do spas insist on them? It turns out there are sound reasons for the lilting synthesisers and echoey melodies. Dr Victoria Williamson, a research fellow in music psychology at Goldsmiths, University of London, explains: "A lot of this works on a very basic evolutionary level. If you hear a very loud, very sudden, very fast bang, your evolutionary response is for your heartbeat to quicken; you get a little bit of a sweat on, and you get that fight-or-flight response. A lot of music can function in a similar way.
"So if you do the opposite to that, and make the music nicely repetitive so the person knows what's coming, and you make it soft and in the lower registers of volume, and you play it in such a way in which it would probably be described as smooth shapes, with no jolting articulation, then you will get the reverse response." Indeed, research conducted in the US has revealed just how much music can affect the mind and body. Dr Claudius Conrad, a senior surgical resident at Harvard Medical School, for example, found that post-operative patients who listened to an hour of Mozart at a slow beat experienced an easing of their blood pressure and heart rates, and showed a 50 per cent spike in pituitary growth.
The traditional, gentle music favoured by spas ticks all the boxes, with its soft, slow rhythm, its meditative style and endlessly repeated phrases. According to the scientific research, it should be lowering my heart rate, calming my breathing and reducing me to a zen-like state. So why isn't it working? Does my irritable response make me a scientific anomaly, incapable of responding to a basic trigger?
On the contrary, says Dr Williamson. The science is not that simple. Crucially, our response to music is also affected by our personality and tastes, and by what is familiar to us. "All the things I've said about loud versus soft and smoothly articulated sounds versus roughly articulated ones are generalisations. They will not apply to everybody and even if they did apply to everybody, they won't apply to everybody in every situation. It can vary according to who you are, but also what state you're in at any one time, as well as your individual preferences and your familiarity with the music."
The upshot is that if you don't like what you're hearing, it's unlikely to relax you. This is confirmed by the findings of a study by Dr Michael Miller at the University of Maryland Medical Center. He found that among patients listening to their favourite song, the tissue in their blood vessels dilated and their blood flow increased, whereas subjects who were played music they disliked experienced a narrowing of their blood vessels by six per cent.
If music has such a profound and immediate effect on our psychology and physiology, perhaps spas should be reviewing their one-track-fits-all approach. In fact, it transpires that "elevator" music is not universal. Jennifer, a spa reviewer, has discovered that not all spas use those familiar, watery sounds. The results, sadly, aren't always an improvement. "In Italy, I loved having a treatment to Italian opera, and in an eco-spa in Queensland the beats of the local tribe's drums and didgeridoo were wonderful. However, I'm currently based in India and the other day I had a massage to the (way too loud) sounds of bhangra music, and it just wasn't conducive with a spa environment."
One solution, of course, could be to cut the music altogether. Caroline Carswell, 39, is deaf and removes her hearing aids altogether when she's having a treatment. "I like a quiet massage", she explains. "It's something to do with the zone-out thing, I think." There may be practical reasons, however, for having some sound piped in. Jennifer points out that a silent spa can be equally offensive. "Not only do you hear every footstep the therapist takes, every swallow they make and every noise from the reception outside, the point of a spa treatment is to relax you to a point where you can fall asleep. If you are in fear of your snores and heavy breathing, that's not likely to happen."
The answer might be to follow the example of Dr Conrad. He asks his patients in the surgical intensive care unit which music they would prefer, and it seems it doesn't matter greatly what they choose, so long as they enjoy it. But what if your taste extends to something loud and jarring such as heavy metal? Could that still have a positive effect? Dr Williamson doesn't rule it out. "Anything you are particularly familiar with will promote a safe environment. You could argue that you would feel more relaxed than if you were faced with an environment with which you were completely unfamiliar."
Happily, some spas recognise the importance of personal preference. At the Amara spa at the Park Hyatt Dubai, and Akaru at the Dubai Aviation Club, clients can choose their own music from a menu designed to complement the type of massage, while some even encourage you to bring your own. "I went to a spa in San Francisco this summer," says Sarah Drew Jones, 43, "and they asked me when I booked if I wanted to play my own CD. It was the first time I'd ever been asked, but it's a good idea."
So the next time you're having a hot-stone massage, bring your iPod just in case. And if you hear the delicate strains of Motörhead or Metallica coming from the adjoining room, you'll know what's going on.