Rates of exchange tend to wobble even more erratically than the antique baggage trolleys at Gondar airport in the Ethiopian highlands. Had you been blessed with a wad of US dollars and plenty of foresight five years ago, you could have bought euros when they first appeared in 2002 and smugly watched their value increase by 50 per cent against the American currency. The dollar is performing so feebly on the FX (foreign exchange) front that even that comedy currency, the Cuban convertible peso, has appreciated against it.
Some rates, though, remain constant. For as long as I can remember, the Bahamian dollar has been at parity with the US version; 3.6725 UAE dirhams equal US$1; and, mixing arithmetic with aesthetics, one picture has long been held to be worth 1,000 words. Yet one dimension to travel is even more valuable: the soundtrack of a location.
Take all the pictures you like, but to capture properly the spirit of a place, you also need noise.
Eight days ago, the high-altitude city of Gondar celebrated Meskel, the festival of the finding of the True Cross. The tangled legend that justifies the jubilation involves a mission from Ethiopia – one of the first nations to embrace Christianity – to the Holy Land to procure a piece of the cross used for Christ's crucifixion.
The main ceremony takes place beneath the walls of Gondar's fortress. At the climax of the festivities a huge cone of firewood topped with a cross is set ablaze. This takes place at noon, which reduces the visual impact somewhat. But the aural experience is astonishing. The drums, the chants, the shrieks and squawks, the urgently whispered solicitations to "give money, one birr", combine to produce a complex cacophony.
As I walked through the backstreets, motor vehicles were notable by their absence – in the main, Africa walks. Instead of traffic, the chorus line comprised cackling birds, complaining livestock and chirruping mobile phones.
I recorded the sound scenery on an MP3 player, and you can hear a short burst right now (so long as you have an internet connection a mite faster than those in Ethiopia); click here to listen.
"FX" stands for more than foreign exchange: it also means sound effects. The BBC appreciates how much of a pleasure noise can be, which is why it maintains the world's finest library of recorded sound effects. Despite the controversy over what one newspaper called "BBC cons", the corporation quite rightly devotes time and money to pretending people are where they are not.
Listen. If you are in a city, you may hear a gentle background rumble. You can hear a similar rumble from time to time on Radio 4. "City Skyline" is the name of this soundtrack. And where was it recorded? Niagara Falls. The sound of the cascade, slowed down, serves perfectly to place a bunch of actors in an outdoor, urban setting when in fact they are in a studio.
The BBC dispatches sound recordists across the globe. For example, one CD is labelled "Urban South America". It was recorded on both sides of the Andes in 1991. Suppose Radio 4 wants to dramatise Graham Greene's time in Asunció*, the capital of Paraguay, where he wrote Travels with My Aunt. The actual sound emitted by the country's steam-hauled train would prove invaluable.
If you were listening to Radio 4's Excess Baggage programme a few Saturdays ago, you would have heard precisely that sound. We sent Rob Crossan to report from Paraguay on the ultimate budget-travel destination. Excess Baggage picked up on the idea, and interviewed Rob about his trip. And to introduce him, they used the sound of that same steam train – which, in 1991, happened to provide the link between Asunció* and its airport. As the train puffed along, the sound engineer hung on for dear life to some expensive recording equipment, while feeling like grim death after an unpleasant encounter with some dodgy in-flight catering on the late and unlamented Venezuelan airline, Viasa. I know that because I was that recordist.
Although I am no longer a BBC sound engineer, I still adore the sounds of the city. A fortnight ago, I broadcast live as part of the Mo Dutta show on BBC Radio 2 via a satellite link from a garden in Addis Ababa.
The melodious morning birdsong was augmented by percussion provided by the panel-beating workshop next door, while the local broom-vendor turned up on backing vocals. But not everyone was entirely convinced by this garden of Ethiopian delights. The producer, Anthony Dunning, e-mailed afterwards to say: "We had one listener who thought we made up the whole Ethiopia thing on the grounds that the link sounded too good and there wasn't enough of a delay."
The many tongues of evil
"If you are discreet with smaller amounts [of marijuana], you are probably OK," says the first Lonely Planet book, Across Asia on the Cheap. The country in question is Afghanistan, where "small busts can be bribed out of".
The world has moved on – and not just the attitudes of the Afghan authorities, or the desirability of travel there. The company that advised visitors to Nicaragua that "if you get robbed, the thieves do not usually take your passport or underwear", and warned that a financially savvy Catholic mission in Uganda offered "worse rates than bank rates", has been taken over by the BBC's commercial arm, BBC Worldwide.
Tony Wheeler, who founded Lonely Planet with his wife, Maureen, recently celebrated his 60th birthday. But he shows no sign of slowing down. He flew in from Australia to publicise his latest book, Badlands, which he says is based on an original idea by President Bush.
"As soon as he mapped out this 'axis of evil', I thought, 'I've got to go there'. So I went to Iran, Iraq and North Korea." He then chose a few more "countries that people disapprove of", including Cuba, Afghanistan and Libya. "And then I threw in Albania, just for the fun of it."
The foreign-language editions are now appearing – with sharply divergent titles. The Dutch version, Schurkenstaten, translates laboriously as " Countries Where Scoundrels Govern", while the Italian title, Stati Canaglia, can be interpreted as "Naughty Nations". Sometimes, English can be wonderfully concise and direct.