This article details a process I used to create a feature-rich, free drum synthesizer which incorporates a physical input device (you get to bang on something) a VST software module to translate the physical input into MIDI information, and a VSTi sampler to translate MIDI data into realistic sounding drums.
This article draws heavily on information obtained from a number of Internet resources, some of which I remember the names of and have included in the References section of this post. I do not mean to steal this information from the originators, but hopefully refine it into something that can be used by the relative newcomer to digital recording. Much of the source material and the domain information for drum triggering gets VERY in-depth and can be seen as a (very fun) rabbit hole should you start to dig deeper. I hope to “nutshell” this information so that the user knows which portions of what they see are important for them to understand at this point in their musical journey.
Furthermore, this post is part one and I plan to get more in-depth on the “feature-rich” aspect of this setup. At the end of this instructable you should have a single working
drum trigger and be able to make it sound like a loud snare or bass drum when you strike it. Varying loudness (dynamics in audio terms velocity in MIDI terms) will be dealt with
in a followup.
Recipe for one “drum”:
Piezo-electric element (I got mine from Radioshack and eBay, remove any plastic casing around the element)
Two-wire Audio cable with bare wires on one end (I sacrificed an old guitar cable and stripped the wires back a bit)
Stack of notecards of any size. (Don’t open them, leave the plastic cellophane on)
Free VSTi instrument plugin shortcircuit – http://vemberaudio.se/shortcircuit.php
Free Audio signal to MIDI trigger VST plugin – KTDrumTrigger http://www.smartelectronix.com/~koen/KTDrumTrigger/
Audio Interface that accepts input from audio cable mentioned above. (In my case the intact 1/4″ mono plug from my guitar cable)
Digital Audio workstation with MIDI support (including editor and record capabilities) and VST support.
Audio Sample for the “loudest note” on the particular piece of kit you are looking to emulate. (For instance a snare sample recording the hardest hit, whether recorded by you or gotten from somewhere
Please note that I am using Samplitude Silver (free download at http://dl03.magix.net/samplitude_silver_soundcloud_us.exe?cookietest=1) to demonstrate this method. You might have to make some adjustments to the process if you are using a different DAW, but the method itself is indeed portable.
1. Build and test your input device
a. Wire the piezo-electric element to your two-wire audio cable. Use whatever means you have/are comfortable with. (I initially just twisted the wires together and held them together with electrical tape, I recommend a more permanent solution. 🙂 ) Be sure that the piezo element disk itself is freely accessible and somewhat moveable. (I left a little of the raw wire some play past the shielding on the cut end of the guitar cable)
b. Load up your computer and DAW. Add a mono audio track and mark it as the track you will be recording to, selecting an input on your Interface.
c. Test the signal by plugging the non-piezo element end of your trigger into your audio interface’s appropriate input. Start a recording and LIGHTLY tap on the piezo element.
You should see (and possibly hear) some “clicks” or “pops” on the audio track. If you do not, try raising the input gain on your interface and repeat the experiment. If you have pulled the gain up quite a ways and still see no signal, double-check first that you have marked the correct input from your interface as the record source for the track, then your wiring job.
d. Once you are sure you are seeing or hearing the “thumps”, stop and cancel/undo the record of that audio.
3. Mount the input device
a. Take your unopened plastic-wrapped stack of note cards in hand. Cut a slit in the plastic (toward the middle of the stack) such that you could slip the piezo element in between the cards.
b. Do just that, slide the piezo element somewhere in the middle of the stack. You don’t have to get it into the dead center, don’t go too crazy. Also, as long as all of the piezo disk and maybe about 1/4″ of wire lead is “in” the notecard stack, you should be good.
2. Calibrate the input + audio interface combination
a. Enable and begin recording again in your DAW with the input device as the record source. Hopefully you will see that your piezo is still wired up correctly and that inserting it into the notepad stack has not caused it to stop working. You may notice that when you tap on the notecards it seems either louder or quieter than when you tapped on it before. This is why we are calibrating this guy.
b. With your notecard stack on a secure hard surface, tap on the notecard with your finger or some other implement (like a pencil). Move the tap around the notecard and watch/listen to what it does to the input signal. You may find that if you tap right over the spot where the piezo is, that the signal clips, or that if you hit it too hard the signal clips. This means the volume is up too high (or you are hitting it too hard/too close to the piezo). Adjust the gain on your audio interface until you feel like you are hitting the cards as hard as you would like in the spot you would like for the “loudest” drum hit when recording without clipping. Once you have found the sweet spot, write it down somewhere for future reference. (For me it was gain at about 11 o’clock, hitting right over the piezo for hardest notes using my finger). You will find that this primitive device you just built can actually handle a pretty wide range of dynamics and that you can get different results by moving your “striking object” around the notecards and hitting at different levels. Find a good general location on the notecards to strike and somehow mark it (I used a little circle sticker showing the rough center of the “target zone”).
c. Stop the recording in the DAW and cancel/undo to leave a blank track.
4. Record a simple “bass drum beat” with your newly constructed notecard drum. It’s going to record just the “clicks” or “tap sounds” made from striking it. Try recording some as quiter hits and some as louder ones. This should be natural if you just pretend you are really playing a drum beat on the cards some hits will be harder and others less emphasized.
5. Translate audio input into MIDI with KTDrumTrigger (one of the more complicated portions of this instructable).
6. “Print” the audio track to the MIDI track via recording and KTDrumTrigger.
7. Configure shortcircuit to play the MIDI back, triggering your sample at each MIDI event.
Extra Credit: Try to see if you can get realtime Audio -> MIDI recording going, without the need for the interim audio track. This is often a function of enabling particular settings for “Realtime Effects monitoring” in your DAW and routing the signal from KTDrumTrigger directly to a MIDI track.
Source for most of the information on shortcircuit as a drum sampler – http://stash.reaper.fm/2313/Shortcircuit%20Drums%20for%20REAPER.pdf