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Koen Tanghe @ Smartelectronix
KTDrumTrigger

Description

This is how it looks like

KTDrumTrigger is a VST plugin with custom editor that triggers MIDI notes based on the sound level of the incoming audio stream in different frequency bands. It allows you to "detect" occurrences of percussive sounds in an audio stream and send out a MIDI event whenever that happens.

It works like this: incoming (mono) audio is split up into different frequency bands using three tweakable filters. The signal in each of these bands is sent through an envelope follower. When the envelope reaches a specified threshold level, a MIDI note on message is generated. The trigger module has some built-in hysteresis and minimum inter onset time settings to avoid fast successive triggers due to noise on the envelope curves. Visual feedback of the filter and trigger settings is available....

Note that this is a rather simple system for finding drum onsets in an audio stream. It will probably only work reliably on isolated drum tracks (no mixed-in music), it's quite sensitive to volume changes and it might not always be possible to separate the different types of drum sounds using simple filters. However, if you just need a fast way of transcribing your isolated drum tracks into MIDI so you can tweak them further or apply the groove to other parts, it might well do the trick and save you a lot of time :-)

That said, no one says you *must* use this on drum tracks! You might come up with some other applications where this thing comes in handy or use it to extract a rhythmic sequence out of an instrument track (although this will only work with instruments that have clear onsets). As always: tweak those knobs and experiment!

Download
File Description Size Date
KTDrumTrigger1.0b5_VST_win32.zip Version 1.0 beta 5
Windows, VST, dll
264 KB 20060808
KTDrumTrigger1.0b5_VST_win32.exe Version 1.0 beta 5
Windows, VST, installer
582 KB 20060808

Changes for version 1.0b5:
- sharper filters
- support for 24 channels
- possibility to enable/disable channels
Notes:
Presets are incompatible with previous versions. Use at your own risk. If you find a bug, please let me know.
Mac versions not available yet.
And before someone asks: indeed, 1.0b4 was never released publicly...

KTDrumTrigger1.0b3_VST_OSX.dmg Version 1.0 beta 3 *
MacOSX, VST, PPC only
338 KB 20050306

Changes for version 1.0b3:
- support for velocity sensitivity
- added MIDI compander for controlling MIDI velocity
- fixed bug in GUI (animated plots)
Notes:
Presets are incompatible with previous versions. Use at your own risk. If you find a bug, please let me know.

Note regarding Mac Universal Binary versions
Spending some time and efforts to make the VST Universal Binary versions happen is on my to do list. But most of my time is spent on other things at the moment, so don't get your hopes up too high...

* Thanks to Sophia Poirier from DestroyFX for building the Mac versions !

Some hints to get started
  • You will need to find out how to route the MIDI output of the plugin to the MIDI track or instrument you want it to be sent to. This is different in every host:
    - in track-based hosts (like Cubase), inserting the plugin on a mono audio track will usually add the plugin to the list of available MIDI inputs for your MIDI tracks
    - in modular hosts (like Bidule), you will see 1 input (audio) and 2 outputs (1 audio and 1 MIDI): just plug in two audio cables and a MIDI cable and you're all set
  • A more detailed description of how to setup KTDrumTrigger in your host can be found over here. This document also contains a list of hosts that currently don't support this type of plugin.
    A screen shot of a setup in Cubase SX 1 can be found over here.
    A screen shot of a setup in FLStudio 9 can be found over here.
  • Since there are three "channel strips" in the plugin, your audio track can contain three types of drum sounds that are spread over three different frequency ranges on a single track. If you really need more, just put the audio output mode on "through" and insert another instance of the plugin after the first one.
  • For bass drums, use a low pass filter with a very low cutoff frequency.
  • For hi hats, use a high pass filter with a very high cutoff frequency and a high Q factor.
  • Snare drums can be tricky as they contain both low and mid (to high) frequencies. Use a band pass filter with reasonable Q factor and try to find the cutoff frequency where you can see the biggest difference between peaks caused by bass drums (and maybe hi hats) and snare drums. After that, set the threshold so that it is just above the non-snare drum peaks.
  • If you get false triggers due to noise on the envelopes, increase the attack and/or release parameters of the envelope follower.
  • The IOT and hysteresis parameters can help eliminate false triggers further by limiting the possibility of having multiple triggers too close to each other.
  • Experiment for yourself and if you want more info on the parameters, read that "read me" file if you didn't already...

Demo examples
Audio MIDI Info
beatboxing [2.2 MB] N/A This is a great demo made by ModuLR and demonstrates how KTDrumTrigger can be used for turning beatboxing into synthesized percussion. More info on how he did this can be found in this thread on KVR.
test1.mp3 [113 KB] test1.mid [1 KB] A simple single track drum fragment converted to MIDI (BD, SD and CH).
test2.mp3 [105 KB] test2.mid [1 KB]

In the picture below you can see a very simple experimental setup I did at home on my desk, just to see if it could work. I routed the audio picked up by the microphone through a single instance of KTDrumTrigger with one low pass filter and one high pass filter and recorded the generated MIDI back to a track in Cubase.

  1. An empty shoe box with a mouse mat on top (use the backside of the mat to get a muffled sound).
  2. An almost empty can of transparent metal varnish (anything that will produce sounds with higher frequencies when hit).
  3. A simple microphone.
  4. Two old drum sticks.
test3.mp3 [28 KB] test3.mid [1 KB] Another simple single track drum fragment converted to MIDI (BD, SD and CH).

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