You've got your sample, and now you need to tame it and make it do your every bidding. Highs and lows of sample looping, trimming and bandwidth squeezing...

Why edit? We'll be covering creative edits later, but this month we're looking at using editing to save memory.

Creative edits are there to make more interesting sounds. Basic editing has its creative side too, but mainly we're after one thing here - more memory. If you're lucky enough to have an Emulator IV with 128Mb installed you probably won't be that bothered, but owners of an older 2Mb machines will want to get as much out of their hardware as they can.

Before editing you should get into the habit of saving your sample to disk. At the beginning and every time you make a major change, it saves time and aggravation later, after you've just deleted the best bass sound this side of Run DMC and there is no way that you can get it back.

Top and tail

Most samplers give you start and end-point markers that you can place anywhere within the sample. The sample then plays from the start marker and stops at the end. Even if more of the sample has been recorded, you never hear it.

Some samplers give you a graphic display of what's going on. This can be really useful: you can see where the peaks in the sound are, so it's easier to guess where you need to put the start and end markers. Computers are even easier, many people do all their editing work on a computer before transferring the edited sample to a sampler. Other older machines just give you a set of numbers to deal with. Numbers are harder to work with than graphic displays, but you'll get a feel for using them after a while.

Once you've topped and tailed a sound, why keep the extra bits? They're just sitting there taking up space, making your disk-load times longer than they need to be, and generally being as useful as a steak-and-kidney pie at a vegetarian wedding. All but the most basic samplers include a 'trim' feature to remove the dead wood. Hit the Trim button and the space outside the start and end markers is deleted and the memory freed.

You can also use it creatively. If you sample a drum loop, you can use the trim function to make lots of samples from a single one. You can then string these together again in the way that you want. Try doing the same thing with words.

Feel the bandwidth

On some samplers you can set the bandwidth when you sample, on others you can also set it afterwards. This is known as 're-sampling'. You tell the machine the new rate and it converts the sample for you. This can take a while - it's not an instant change like trimming.

Some samplers have limited bandwidth ranges. Some Akai machines only go down to 10kHz, for example.

Loop guru

This is where a visual editing system can really come into its own. It's a lot easier if you can see the loops, rather than dealing with just a couple of numbers. Most recent samplers include an 'auto-loop' option that attempts to find the best loop points, but if all else fails there are a couple of things you can do to make looping easier.

The first step to finding a good loop is to guess roughly where you want it to be. To make the loop as smooth as possible, the start and end sections need to be roughly the same volume and roughly the same timbre. Volume is easy to check, especially with a graphic display. Timbre is harder to manage. Sometimes you have to settle for a bit of a warble in the loop no matter what you do.

The next step is to set the loop start and end points, and the loop mode. Some samplers give you a choice here - you can play the loop forwards, backwards, or have it cycle in alternate directions (see the diagram above). You can sometimes also define whether the loop will play only while you hold a key down, or also when you release it. You may be able to set the loop duration, so that it plays for a set time or just goes on indefinitely. Somewhere among all this lot you'll find a couple of non-looped playback options, too, such as 'play until release' (used for stuttering sampled effects) and 'play to loop end', which plays the whole sample even if you only tap a key.

Once you've got the basics set up, you need to find a good loop. A good loop doesn't go 'click' or 'thud' at the join and sounds as smooth and seamless as possible. You need to match the sample at the start of the loop with the sample at the end. If they're a long way apart you get a nasty click. If you're working with a single note of an instrument, look for two areas where the sound is similar and put your loop points at each of them. For example, a flute sound has similar cycles towards the end of a note, so loop across these to produce a sample with a steady, realistic sustain.

Traditionally, the best place to match samples is at 'zero crossings' - where the samples cross the middle line. If your sampler has a 'find loop' feature this is one of the things it looks for. Zero crossings are fine, but the important thing is that you get a smooth curve across the join. It doesn't really matter how you do this. And even a good zero-crossing loop will sound wrong if the start and end points aren't roughly in the right place. While you're creating a loop you need to listen to it to see if it works musically, and not rely solely on the visual information.

Looping on a non-visual sampler is a pain. To make up for this, a lot of recent machines have a loop-finding feature. You set up the start and end points, or start and duration, and then the sampler tries to work out where the best loop is. Often this works very well, and it certainly saves you time. Others have a 'scrub' feature that enables you to shuffle the loop points (like a DJ moving a record to find a beat) until you're happy.

Sometimes a loop that works musically just won't settle in and stop clicking. If the effect isn't too bad, you can try 'crossfading' across the loop join. This does exactly what you'd expect - it takes some sound from the end of the loop, fades it in at the start, and vice versa. This can be a quick fix, but it only works if the loop is roughly right to start with.

One final option you may come across is loop 'tuning'. Sometimes loops end up sharp or flat compared to the rest of the sound. With a loop-tuning feature you can correct this. You can also use it to create special effects.