Simply put, a VDL template is basically just a blank file you launch in your notation program. While this seems unspectacular, this file is helpful because it understands how your Virtual Drumline instruments are mapped. What does that mean? Well, "percussion mapping" is an important concept to understand when writing unpitched percussion music using notation programs like Finale or Sibelius.
Here's an example. Let's say your VDL snare drum sounds a right-handed strike by entering a G#, and it plays a left-handed strike by entering an F#. Naturally, you don't want your snare music to appear on two lines (let alone with sharps!). Using percussion mapping, your notation program will play those F# and G# notes so you'll hear the right-to-left playback (or rim shots, buzzes, rim clicks, press strokes, stick clicks, or countless other options!), but they'll display on the score as a typical one-lined snare part with suitable noteheads.
Since much of VDL consists of unpitched percussion instruments with deep detail, VDL templates for Finale and Sibelius have been a very helpful tool for many VDL users. Finale and Sibelius both give you the power to control percussion mapping yourself. It can be a tedious process, but the programs allow you to handle this. For those who'd rather not fuss with the time it takes to build these templates and percussion maps, VDL templates can be purchased from third-party template developers like The Write Score.
Get a discount on your template at The Write Score by entering the promo code: TAPSPACE10.