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Auto-sample Your Synths In MainStage

Apple Logic Tips & Techniques By Geoff Smith
Published October 2018

Screen 1: The Auto Sampler’s plug‑in GUI allows you a lot of control over the auto‑sampling process. Here it’s configured to sample every three semitones and the Auto Loop parameter is set to ‘Search’ so it automatically finds the best loop points.Screen 1: The Auto Sampler’s plug‑in GUI allows you a lot of control over the auto‑sampling process. Here it’s configured to sample every three semitones and the Auto Loop parameter is set to ‘Search’ so it automatically finds the best loop points.

Turn hardware monosynths into software polysynths by auto‑sampling in Logic’s companion app, MainStage.

If you own one of the many analogue monosynths from companies like Moog, Korg or Behringer and have dreamt of having a polyphonic version of that synth then auto‑sampling could be a great way to explore some of those possibilities.

In 2012 Apple acquired the Italian company Redmatica and their Auto Sampler, Keymap Pro and EXS Manager software titles. However, it wasn’t until 2015, with the release of MainStage 3.1, that we saw Apple put that technology into one of their products. In this month’s Logic workshop we look at how to auto‑sample hardware synthesizers to create EXS24 patches which can then be used in Logic. If you don’t already own MainStage, it’s a bargain at £28.99$29.99 — even if you just used the Auto Sampler and none of its other features, it still represents excellent value for money when compared to buying other equivalent auto‑sampling packages.


To begin, you will need to connect the MIDI out of your computer to your synth’s MIDI in so that MainStage can send your MIDI Notes to trigger voices to sample. You will also need to connect the audio output of your synthesizer to the audio input of your audio interface. Open MainStage, go to File / New and from the Concert selection pop‑up go to the Keyboards tab, then select the Keyboard option and click the Choose button. If MainStage loads the template in full screen mode simply click the X in the top left‑hand corner to exit Perform mode and enter Edit mode. Lastly, go to MainStage 3 / Preferences / Audio and set the Audio Output and Audio Input fields to the audio interface your synth is plugged into.

Channel Setup

Now your connections are all set up, let’s add a channel strip to carry out the auto‑sampling. Click on the plus button at the top‑right of the Channel Strip Mixer UI to bring up the new Channel Strip pop‑up, and set the Type to External Instrument. Then configure the audio and MIDI port options to reflect the connections to your synth. Lastly, click Create. (I found a bug present where the audio input I set in the pop‑up didn’t set the audio input on the channel strip. To fix this, go to the Input field of the channel strip and set it again in there.) Next, add the Auto Sampler by clicking on the first insert slot in your new external instrument channel strip, then go to Utility / Auto Sampler.

The Auto Sampler UI is divided into sections — click on the keyboard to check that your synth is set up correctly and receiving MIDI. As you play notes from the keyboard you should be able to monitor the output of the synth coming into the Auto Sampler. Play a selection of notes from the full range of the keyboard and check that no note drives the input into distortion. To avoid the risk of distortion, I always aim to leave at least 6dB of headroom.

Let’s begin sampling with a single oscillator from an analogue synth. I’m using my Moog Sub37, however you can use any synth from which you like the raw character of the oscillators. Set up the synth so that you have the sound of a single, raw oscillator. If the synth has an equivalent of an ‘init’ or ‘default’ patch with all the modulation and effects turned off then load that. If not, turn all the other oscillators off or down, then set all the LFO and envelope modulation to be equivalent to zero (or off) and, lastly, bypass any effects.

Setting Parameters

Now that our synth sound is ready for sampling, let’s look at the basic parameters of the Auto Sampler. Set the note range parameters Range Start and Range End to encapsulate the lowest and highest note you will ever want to play, I generally set this from C0 to C7 (see Screen 1, above). Set the Sample Every parameter to three semitones; this will give you a relatively high frequency of sampling but each octave will maintain a similar sample transposition factor. As we are sampling a single periodic waveform we can drop the Sustain parameter down from 10 seconds to a lower value, I used a value of 6 seconds but it could easily be lower.

Setting the Auto Loop parameter requires some thought as it specifies how the Auto Sampler will approach automatically looping the sample and should be set according to the type of patch you are sampling. For a simple periodic waveform like the one we are trying to sample it is relatively easy to loop as it just requires the loop points to be set at zero‑crossing points — a number of whole cycles of the periodic waveform apart. Luckily for us the ‘Auto Loop : Search’ setting does exactly that. This option will find the best loop points in your sample but won’t apply any crossfade looping or clever processing of the loop points that the ‘Penrose Machine’ or ‘Search with Rev Fade’ options would. Whilst these techniques can help create seamless loops with complex material, on simple waveforms they can introduce unnecessary artifacts so are best avoided. Lastly, press the Sample button to begin your auto‑sampling. You will get a helpful read‑out on the Auto Sampler’s plug‑in UI that shows the waveform as it's being recorded and the time remaining to complete the sampling operation. Use this time wisely. I suggest making a cup of tea.

To try out your sampler instrument, go to the plus symbol to bring up the New Channel Strip pop‑up and create an Instrument channel strip. Put an instance of the EXS24 sampler in the Input slot. From the preset menu you should see an ‘Auto Sampled’ category in the hierarchical menu. All the auto‑sampled patches you create will go into here. If a patch is not displayed, use the Refresh Menu command and try again. If you’re happy with the result, sample all of the basic single waveforms from your synth that you want.

Combo Bonus

Next, it’s worth sampling combinations of oscillators with detuning, as these can make excellent building blocks when creating sampler patches. The way an analogue synth combines waveforms and how they drift can often sound quite different to recreating that effect using the modulation section of the ESX24. Once again, there’s only a small amount of change in the waveform over time so you can generally get good results using the ‘Search’ setting for the Auto Loop.

It’s also worth experimenting with the Round Robin parameter. If your synth’s oscillators are free running, every time you press a note they will start from a slightly different place and hence sound a little different to the previous note. When you’re combining two or three oscillators together this starts to become more obvious. Try setting the Round Robin parameter to four. Now, the Auto Sampler will capture each note range four times, and when you play each note the EXS24 will automatically cycle through the four samples, creating more variation and making the end result closer to your original analogue synth. Be aware though this will multiply by four the time taken to sample and the amount of memory used by the patch. More tea is, therefore, required.

Patch Work

Lastly, the Auto Sampler can be reasonably effective at capturing full patches from your synth. Choose a preset and once again make sure all of the effects are bypassed, but leave all of the envelope and LFO modulation as is. Set the Auto Loop parameter to the ‘Penrose Machine’ setting. The Penrose Machine creates a DSP‑synthesized loop from a snapshot of your sample and can generally produce a reasonable loop from most sounds you can throw at it. If you haven’t tried it before, the results are quite astounding especially when you consider how much work it would take to achieve a similar outcome manually.

Screen 2: In order to capture a complex synth patch with a lot of modulation you can configure the Auto Sampler to sample at different velocity ranges using the Velocity Layers parameter. For complex patches use the Auto Loop: Penrose Machine setting to automatically loop the samples.Screen 2: In order to capture a complex synth patch with a lot of modulation you can configure the Auto Sampler to sample at different velocity ranges using the Velocity Layers parameter. For complex patches use the Auto Loop: Penrose Machine setting to automatically loop the samples.

You may also want to capture the velocity response of a patch. For example, the patch you are sampling may open the filter cutoff as the velocity increases. Set the Velocity Layers parameter to a value greater than 1. As a general guide, four velocity layers will give you a workable approximation of your patch, whereas eight velocity layers should be enough to achieve a realistic version on all but the most sensitive material (see Screen 2). As with round robins, the downside of adding more velocity layers is it will take longer to sample the patch and it will use considerably more RAM when loaded into the EXS24. If your hardware synth has a sampling and synthesis architecture with different keymaps for different velocity ranges, then it’s worth matching the velocity switching in your synth with that in the Auto Sampler.

Next time, we look at how to use your EXS24 patches in Track Stacks and how to add them to Logic’s powerhouse synth, Alchemy.  

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