Playing It Straight
Adding some randomisation (whether by design or accident) is all very well, but what about making well-planned adjustments? Let’s start with an 8th-note hi-hat pattern:
As you can see, this is about as rigid as it gets; there’s no variation in velocity or timing. In terms of the auditory system, varying the loudness of similarly-toned sounds makes the quieter ones appear to come from further away. Sound from further away takes longer to get to the ear (very approximately 1 millisecond for every foot of distance), so in our fixed pattern above it’s possible to fool the brain that there’s a variation in timing by altering the relative loudness of some of the hats. Here we reduce the level of every other beat slightly:
And then the same effect applied more heavily:
More complex variations make for a further enhanced groove. Here’s another regular pattern of velocity but with multiple levels across each bar:
A similar effect can be achieved by applying a low-pass filter to some hits. High frequency sound attenuates more quickly than lower frequencies due to their relative energy level and the ease with which the less powerful high-frequency changes are absorbed.
So, once again, two similar sounds with differing high-frequency content will be perceived as coming from different depths in the sound field. In the next example we’ve mapped velocity to filter cutoff. High velocities let all frequencies through, whilst lower velocities increasingly remove top-end:
Once again, we can use more complex patterns of velocity to create more interesting grooves: