Here are some different approaches I thought of:
Firstly, what is the geographic location of the desert you have in mind? There are many different types of deserts, and different regional cultures within the same desert (such as the African Sahara --just think of the vast number of African people groups it spans) will have different music styles --different instruments, different rhythmic patterns played on common instruments...the list goes on and on. I would advise doing some research and picking a specific location and cultural group if you are aiming for accuracy.
Also, as with any composition work you will ever do, the "feel"/situation/idea/viewpoint you are trying to portray/depict/suggest (I couldn't pick just one word, hence the forward slashes). A peaceful moment at a stereotypical oasis will (or should!) sound much different from a sandstorm, long and laborious camel caravan trek, unexpected rain, or bitterly cold and dark night. A work that attempts to follow a lost, dehydrated wanderer's encounters with various mirages will have a completely different feel than that illustrating the hectic flight of a desert hare -- and both of those will be written differently than a majestic celebration of the desert's vast landscape itself... and then incorporating indigenous instruments into the mix, as well as typical regional rhythmic patterns, time sigs, scales, etc. will also give the piece a unique flavor.
Going with the stereotype
Disney definitely made broad use of the Middle-Eastern desert stereotype (and probably helped develop and fuel it) in the movie Aladdin. Luckily for us, many parts of the movie's soundtrack reflects their aims. Some other references I can think of right now/found on the web are Arabian Dances and a marching band show I saw this year (unfortunately I can't think of the name of the show or the band).
My concert band idea
If you're writing this for concert band or something, though, and just trying to achieve the stereotypical, instantly-recognizable desert image, here are my ideas on the "desert landscape" thing (I like the concept so much I'll probably try my own hand at this someday):
- Opening movement/section (depending on how long the piece is):
Aerial flyover-type thing....soaring over the endless sand.
Brass play a rousing, broad melody, with woodwinds floating atop with various runs,etc. supporting the brassline, liberal use of cymbal crashes, tasteful tom-tom (and maybe timpani) parts, indigenous instruments support, playing a theme that continues throughout the piece [some kind of cool ostinato-type stuff]
Swooping in to get a closer look at things....
Brass drop out, lightly-scored woodwinds give a more intimate feel than the previous "sweep-over" by the brass. Infrequent but well-placed trills accent the cultural-region-contributed syncopation, if any. Marimbas play some kind of slightly syncopated, cultural-region-based pattern, shakers or whatever indigenous instruments are highlighted occasionally and are used as the main percussion/rhythmic-drive force now (bass drum, timpani, snare, and cymbals are a no-go here).
Desert animals thing
Following a desert animal...which one, I have no idea
Probably a marimba ensemble feature plus the addition of any indigenous instruments you can think of. What goes on here is dependent on the animal selected. Cabasa is likely a must, unless taking a "savage dismembering" approach.
Lost in the Desert
Great. We're lost. Stereotypical walking-around-in-circles, etc.
Trancelike feel with much shifting of time sigs, accidentals thrown in (shift between scales perhaps, to give that idea of uncertainty and confusion)...Depending on the feel you're going for, perhaps some synthy stuff for mirages. Or maybe play off the fact that they're "illusions" and give the illusion that the phrase is about to resolve and abruptly cut it off with the start of a new phrase, that perhaps repeats but increases tempo each time? This could go in many different directions.
Plunge into darkness.
Eerie vibraphone and French horn stuff, maybe have horns "stop" the bells with hands for hits or something, to give contrast. Native instruments should shine in this passage (in my opinion). Claves or something similar would be neat on a syncopated pattern. Low reeds could sustain. Eventually maybe a bassoon solo.
Daylight, caravan trekking
Leaning heavily on downbeats to suggest the footfalls/gait of the camels.
Here is where the "one TWO-AND three FOUR" (not sure if I got the accents right) would be played by drums (djembe, etc.) and shakers. Maybe sparse use of background winds and pitched percussion to accentuate the "lean" more. Oboe solo, muted trumpet support possibly. The main idea for this section will be the obvious placing of weight on downbeats. Dramatic entrance of French horns leading the brass if going into either the (grossly stereotype-driven) desert raiders scene or the "back-to-the-intro-overview-theme" thing (not listed, because it's like a "swooping back out thing").
[obnoxious stereotype alert] Either desert raiders or marketplace
Depending on which option.....
Desert raiders: Intensity is key here....a lot of tribal-sounding tom-toms....just go with the drama.
Marketplace: Think hectic, think of the market in Aladdin (again, hate to say it, but...). Driving low brass, low reeds stay low except on hits. Saxes and/or clarinets could have melody here, but it really depends. Maybe add in some wild trombone after the melody is well-established. Lots of shakers and hand-drums. Little to no timpani.
Again, this is just a bunch of random stuff I thought of off the top of my head. Now that I read it, it sounds like more of a movie score than a cohesive work, but I might be wrong. And I applaud anyone who read though yet another of my ridiculously long answers. (I honestly try not to make them long...)