Acoustic instruments are marvellous things – we hit them, stroke them, caress notes out of them, and they never swear at us or refuse to make a noise (of some sort, not necessarily the noise we want though). They continuously react with their surroundings (clap your hands with your foot pressing down on the sustain pedal of an acoustic piano and you'll see what I mean), have an infinite dynamic range and every single note they ever play will be different to the last, and every other note that instrument will EVER play.
Some of these characteristics are desirable in electronic instruments, some are not.
Take the china cymbal you have on your acoustic kit (assuming you have one). It is continuously vibrating because of the air movement and floor vibration in the room. Even though it rings for a few seconds after being hit, from the audience perspective, it just goes “Bang!” or “Gaaaa” or “GSSHHHhhhhhh” depending on the model and weight of it, and to them it seems to die away almost instantly.
Take the lovely china sample you have on your electronic kit. That also goes “Bang!” or “Gaaaa” or “GSSHHHhhhhhh”, and if you are lucky enough to have a module that allows you to have nice long cymbal decays, will ring for quite a long time. But do we want that? Well, lets have a look at what happens when we play the pad.
You hit the pad, the module makes the sound which the audience hear and all is good surely? Well, if the audience hear the first half a second, they wont hear (amongst the barrage of toms, kicks and clarinet samples - ok, maybe not) the long decay as the china sound dies away. That long decay is stealing one note which could be doing something else.
If you remember the article I wrote on polyphony, you'll remember that all drum modules have a set polyphony which means they can only play back a certain amount of notes at one time – as many as the processor can handle. If you use up all those notes, then the next note to sound will have to steal one from a sound that is already playing (called note stealing).
This isn't a problems as such, but the easier our modules lives are, the better all round.
But theres another thing. If you play your china sample five time in quick succession, all those decaying 'tails' as the china sound dies away are playing in the background, hidden under the last note you played. This is what happens (to a degree) on a real cymbal but the tails all blur into one as the vibrations bounce around the metal.
There is something we can do about this.
You might have noticed a function inside your module (not all have it but most do) that allows you to switch each sound from 'poly' to 'mono'. Poly is polyphonic (or more than one note at a time) and Mono is monophonic (or one note at a time). Most modules are automatically set to Poly by default, but by carefully choosing Mono for select sounds or pads, you can clean up your stage sound (by not having unnecessary audio tails playing in the background), and lower the demand on your module.
If you imagine hitting your china sample five time in Poly mode, it would look something like this.
If you hit your china five times in Mono mode, it would look like this.
As you can see, in Mono mode, as soon as you hit the second and subsequent hits, the previous on is cut off. While you might hear this in isolation, when the full band is playing, you definitely wont.
You have to be careful selecting which sounds are in mono and which are in poly – choosing the wrong one can make the kit sounds 'jumpy' or 'glitchy'. For more acoustic instrument sounds, leaving the sample in Poly mode will give a more realistic sound, but with more electronic sounds, you can happily drop all manner or drum, cymbal and percussion sounds into Mono mode and it will give you a cleaner sound (as the inaudible tails are not playing) but will also free up notes for the module to use elsewhere.
So, trust your ears, have a listen, and see if you can clean up your on stage sound, and make your module love you more.
Simon Edgoose