This, unfortunately, is a truth which many Hong Kong restaurateurs apparently have yet to grasp.

Fortunes are spent on decor and the development of themes, yet often the only investment in music after buying a sound system is in a mixed bag of CDs of 'easy listening' tunes.

Leaving aside the question of its merits, much of this music has been chronically overexposed in lifts, malls and restaurants, over a period of several years. To many people, it is an instant irritant.

Restaurants use music for many reasons. Those with a strong ethnic theme use it to reinforce the image projected by the decor, which is why you can expect to hear The Three Tenors frequently in an Italian eatery.

And chances are that if you are eating tapas you will be listening to the Gypsy Kings.

Some restaurants opt to do without music altogether, which reduces the level of aural irritation, but most diners seem to prefer to have some background sound to cover lulls in conversation.

The question is how to choose it and programme it so that the music draws customers in rather than chases them out.

The most common and least effective approach is to buy a selection of CDs and leave orchestrating the soundtrack to restaurant staff.

I have lost count of the number of times I have asked a waiter to change a disc about to play for the third time, apparently without anybody working there having noticed the repetition.

A better system, and one for which many operators of restaurant chains opt, is to hand the problem to an outside contractor, as Windy City, which runs the various Dan Ryan's outlets in Asia, has done.

Dan Ryan's Chicago-style restaurants use A.E.I., an American company, which, according to Windy City's Dale Willetts, 'supplies everything from punk, to elevator music to Latin dance music'.

A.E.I. supplies a unique four-track cassette player system which will play only special tapes supplied by the company, ensuring the continuity of the soundtrack is maintained. The system also has a sophisticated ambient sound meter that registers the level of noise in the room and adjusts the volume of the music accordingly.

Mr Willetts says that costs, after buying the equipment, are reasonable, and the jazz programme the company buys provides the right soundtrack for the restaurants' 40s to 50s Chicago theme.

'It's like putting together a play,' he suggests. 'If you get every element right you have a Broadway hit, but if one element is wrong all you have is an ordinary play.' Cafe Deco has a less specific theme than Dan Ryan's, but its music is even more highly programmed, thanks to a decision taken about three years ago by Martin Kniss, executive chef at Cafe Deco.

'We were getting complaints about the music,' says Mr Kniss, 'and it was no fun for the staff. If you hear the same song three or four times per day it gets annoying.' Music, as it happens, is important to Mr Kniss who played guitar semi-professionally before he entered the hospitality industry. He believes it also plays an important role in a restaurant's ambience.

'If a place is playing bad music, that to me is a reason to leave,' Mr Kniss says.

'If it's good I might stay for another coffee.' He set about creating a music library for Cafe Deco to offer constant shifts of style and mood and be easy on the ear while still being interesting to listen to for those feeling inclined to pay closer attention.

'The first rule is no music that is constantly played in [other] public areas. You will never hear Kenny G here.

'I like music which is good and relaxing but has drive to it. It shouldn't dominate.

'I minimise vocals because in some ways they interrupt conversation and I avoid anything depressing,' Mr Kniss added.

Cafe Deco's eclectic menu absolves the restaurant of any obligation to stick with a particular musical style and Mr Kniss chooses his music by spending hours of his spare time in CD stores listening to discs.

Having chosen what he wants, he then re-records his selections on to a new CD using a computer disc writing system.

Over the past three years he has compiled about 300 CDs for the exclusive use of Cafe Deco. Copyright for the music is covered by the annual licence fee paid by all bars and restaurants which play recorded music.

The music blends elements of new age, light jazz and new acoustic music with evergreens from the likes of Frank Sinatra and Ella Fitzgerald.

As you would expect, a fair number of guitar instrumentals are featured from artists such as Tommy Emmanuel, Mark Knopfler and Earl Klugh.

No track features more than once in the whole collection, and the restaurant's sophisticated CD changer system can play more than 11 hours worth of music without repeating itself.

'It's definitely longer than the average sitting time,' says Mr Kniss.

Now instead of getting complaints about the music, Cafe Deco fields inquiries from customers about where they can buy the discs.

According to Mr Kniss, some new restaurants in town are trying to copy his formula.

Few, however, have the time, energy or technology to match his carefully chosen compilations.

The moral seems to be simple.

Getting the music right for a restaurant can be just as hard work as getting the food right.