You can sample any instrument in the orchestra, but then what do you do with it? Andy Honeybone considers the (historically) right and wrong ways of stacking up the sounds.

Orchestration is just as much about synthesisers in a John Williams film score as it is about violas in a string quartet. Its fundamentals are just as applicable to a sampling keyboard and multitrack tape set-up as they are to a 60 piece orchestra. So what is it?

There isn't a simple answer (is there ever?) because orchestration covers such a rag-bag of techniques, talents and intuition. Orchestration can be a process of translation, say from a keyboard to an orchestra, or it can be indivisible from the act of composition where melody and timbre are simultaneously conceived.

In part, orchestration requires a knowledge of the pitch, range and capabilities of every instrument. This area is more generally known as instrumentation. For the synthesist, the pitch of an acoustic instrument is of no consequence as transposition can be effected by simple parameter changes (you used to be able to say 'at the turn of a dial').

Range and capability, however, are particularly important factors for successful synthesis/sampling. It is well known that acoustic instruments take on quite different sounds dependent on the register in which they are playing. So samples can only be stretched so far to cover a certain range. The clarinet, for example, has a shrill upper range but at lower frequencies is very mellow. Historically, the only instruments that have exhibited one waveform over their entire range have been electronic.

Regarding the capabilities of an instrument, it is important to know the physical limitations. A trombone has great difficulty executing trills and hence they are out of character with the instrument. Similarly, a half-octave glissando (slide) would be impossible on a flute. Even if you are a habitual rule-breaker, you need to know the limits that you've got to exceed.

The other main chunk of orchestration is concerned with the blending and contrasting of raw sonic ingredients — being a musical cocktail shaker. At this point, arranging and orchestration become difficult to differentiate other than on the grounds of the size of the operation. Was the inclusion of a muted trumpet on Fine Young Cannibals' "Johnny Come Home" an act of orchestration or arranging? Dream Academy like it to be known that they orchestrate. Perhaps scoring onto paper is the difference — can you have a 'head orchestration'?

The rest of this rambling episode is based on first hand experience of bringing some guest acoustic musicians in on a recording session with the intention of adding a little tonal colour.

If you have some friends who play 'additional' instruments, be very sure to acquaint yourself with their capabilities and sympathies before co-opting their services. Having passed Grade 8 and being leader of a local orchestra is no guarantee that someone can function on less familiar ground.

Be prepared that anyone brought in from outside cannot be expected to be as enthusiastic about your activities as you are. In particular, time is a very valuable commodity both for someone who is giving up a Saturday to help out and for someone who is picking up the rehearsal room bill. In order to save precious time, it is wise that the guest should be familiar with what is expected of them before the event. This generally means dishing out the manuscript well in advance. Depending on the keenness of your collaborator, they may be prepared to transcribe their part from a demo that you have cobbled together on tape. Do check that the backing track is at concert pitch and tell them the key in case their deck plays back at a different speed from yours. A few seconds of the note A preceding the track will help no end.

Of course, you can take a horse to water but you can't make it drink. There is a chance, if you don't really know your guest, that the music you sweated nights over has stayed put in the music case ever since you gave it out.

Interact with your guest from an early stage to find out what range they feel comfortable playing in and learn any peculiarities of the instrument. Ask for a demonstration of the tone of the instrument at different octaves. If you were engaging a professional musician the job would be simpler, albeit more expensive. You would consult a standard work on orchestration such as that by Walter Piston (not a made-up name I assure you), read up the possible range and write the part accordingly. With friends and acquaintances you can't assume that they are up to professional orchestral standards. Asking saves time and embarrassment.

The most rewarding part of being an arranger/orchestrator is hearing your efforts played for the first time. Even if the performance is less than perfect you will know if it's going to work. That first run through will tell you if your transposing's right, if you're in the right octave, if the harmony works, and if the thing hangs together as a whole. Sometimes it does, sometimes not. What can go wrong when you're so well prepared?

You can divide the problems into two categories: the mechanical, and the artistic. The mechanical covers everything up to putting the manuscript paper in front of the musician, and the artistic covers everything subjective that follows.

The events leading to the playing have been well covered above so let's concentrate on the next step. Your guest may not be able to play the piece, has not looked at the music since you delivered it and is apologising, glowing red and getting up the rest of the band's noses. Solution: judge if reasonable rehearsal will remedy things and, if not, remove your guest from the scene, put the episode down to experience, and drag out a synthesiser to fill the gap.

It can happen that the guest plays the part perfectly but it just doesn't seem right. The root of this problem can be the temptation to use instruments that are available rather than those you would choose given a free hand. Sometimes, an acoustic instrument will not blend with a larger-than-life electronic background. This is one for the engineer.

In my murky past, much time and face was lost by trying to swap a part from one instrument played by a guest who couldn't deliver to another played by his friend who had come to see what was going on. Now although the Glenn Miller sound may have been discovered by accident, it's not a good idea to interchange instruments just because they happen to have the same pitch and are available. The first mistake was in writing a jazz violin part for a classical violinist. Violinists like scalar passages in sharp keys with few accidentals. The part in question was in a devil of a key, angular, and highly chromatic. The second mistake was in transferring the part to an oboe. Wind players need to breathe from time to time and there was not even a tiny pause in the part for a quick gasp. The oboe was not really the sound required for a 1930s pastiche anyway. It didn't even sound like early Roxy Music.