Drumagog is the granddaddy of drum replacement tools, and it’s certainly hard to beat for quality and features. However it also costs several hundred dollars, which is a deal breaker for many home studios on a budget.
But there are some great free alternatives. I’ve listed them here in order of my preference, though several features are more important to me (midi output, velocity sensing,) than might be for others.
KTDrumTrigger [VST – Windows/Mac] – KTDrumTrigger generates MIDI events by watching its input for trigger levels. When the volume of the input goes above a threshold, KTDrumTrigger spits out a pre-defined midi note. A key feature, however, (and one that puts it in the same league as Drumagog) is its ability to sense the velocity of the input, and adjust the MIDI output velocty accordingly. And something not seen in Drumagog is KTDrumTrigger’s ability to monitor a single track for input triggers in up to 3 different frequency bands. This lets a single input track drive (say) a kick, snare, and hi-hat. (The demo on the linked site highlights this feature.) I reach for KTDrumTrigger before Drumagog when it’s specifically MIDI triggering that I need.
apTrigga [VST/AU – Windows/Mac] – It’s not completely free, though apulSoft offers a limited free shareware version. But apTrigga is effectively a Drumagog clone for a tenth of the price. While it lacks MIDI note generation, apTrigga does offer a novel “sequenced trigger” mode, something not possible with Drumagog. The plugin can load multiple layers (i.e. samples) and play each in turn on successive input triggers. This allows the creation of some interesting percussive effects. The multiple layers can also be used for dynamics processing, though, supporting up to 9 dynamic levels. While not as detailed as Drumagog’s 48 layers, this is still more than enough to simulate realistic drum dynamics.
Replacer [VST – Windows] – Replacer works with a single sample (or up to 4 samples in the the full version, available for a nominal donation,) and attempts to replicate the dynamics of the input signal. As with Drumagog, one would use this tool to replace a single drum track (i.e. kick, snare, or tom,) at a time. While it doesn’t support MIDI note generation or positional samples, Replacer’s interface is clean and simple, and above all the tool is easy to use when triggering electronic drums. (I.e. when dynamics aren’t important.)
DrumTrig [VST – Windows] – DrumTrig is Drumagog Lite (or perhaps Extra Light.) It makes no attempt to match the output volume to the input volume, and can only trigger a single sample per track (where Drumagog can fire up to 48 different samples, based on velocity and position.) But Drumtrig is free, and couldn’t be easier to use. Add it to the track to be replaced, drop a replacement sample on it, and you’re done.
Peak Freak [VST – Windows] – From the linked page: “PeakFreak is a plugin that converts audio input that falls into a certain frequency and amplitude range into midi notes of a certain length.” There’s not much more to it, but it’s free, and it’s purple.
Synodeia2 [VST – Windows] – Synodeia2 generates MIDI notes based on the pitch of its input. However, it can be “tricked” to work with drums. Lack of velocity sensing, though, means it’s best suited for electronic drums.