Review – Slide Acoustic for Kontakt from Orange Tree Samples



The name says it all: an acoustic guitar played with a slide. A tricky thing to pull off in a sample library, though. We see how Orange Tree Samples’ Kontakt scripting guru Greg Schlaepfer did it.


by Dave Townsend, Jan. 2016


Guitar sample libraries have been around for as long as there have been samplers and sample libraries. Any 1980’s ROMpler had at least one patch named “Guitar”. It’s been in patch numbers 25 through 32 in the General MIDI spec since 1991 and burned into every SoundBlaster ROM. They all sucked, of course, and nobody would ever mistake one for a real guitar.

Part of the problem with faux-guitars is that it’s not enough to simply sample the sound of a guitar. You have to also somehow capture at least a few of the many articulations that guitarists employ to breathe life into a performance.  Among those, nothing is harder to implement in an ergonomically-friendly way than slides.

Slides just don’t fit into the keyboard paradigm, which is all about notes: individual, discrete notes, not the near-infinite number of in-between pitches that constitute a slide or a bend.  Portamento doesn’t count; it doesn’t emulate any instrument other than a synthesizer – or maybe a trombone. Keyboardists have but one device that at least might potentially serve the purpose: the pitch wheel.

Everyone who’s attempted to fake a guitar on a keyboard quickly discovers that the pitch wheel is crucial to making a guitar melody sound reasonably believable. Everyone who’s ever attempted to use a pitch wheel this way also finds out that it’s surprisingly difficult to pull off. There are three main problems with using a pitch wheel to emulate bends and slides.


Why Bends and Slides Sound Fake on a Keyboard

For starters, it’s hard to manually modulate pitch over a specific interval using a plastic crescent attached to a spring-loaded single-turn potentiometer. Unless your requirement is for a consistent interval that you can program your synthesizer’s bend range to, you’re going to find yourself estimating the amount of wheel throw for every pitch bend, only getting close and ultimately having to manually edit pitch bend events in your DAW’s MIDI key editor.

Then there’s the issue of timbre. In “real” instruments, higher notes don’t have the same spectral content as lower notes – they sound different, not just higher-pitched. Kontakt’s pitch-shifting algorithm does not take this into account.

But what’s most problematic is that the pitch wheel controls every note equally, shifting all held notes by exactly the same amount. What if you want to slide a chord from C major into D minor? Doesn’t work! It doesn’t work because the root note needs to move by 2 semitones but the third needs to move by only 1 semitone. Or what if you want to slide just one note while letting the other notes in the chord ring out? Can’t do that, either.

In the past, I’ve resorted to recording multiple tracks of single notes in order to get a sliding chord to sound right. That’s the kind of thing that takes music creation dangerously close to being work.

This is where Kontakt scripting comes in. It is possible, if you’re clever, to write a script that looks at the pitch wheel’s movement and then makes intelligent choices about how to move notes to their target pitches. This ain’t Scripting 101, though, and probably not a good “hello world” project for beginners.

Fortunately, thanks to the efforts of scripting guru (and Orange Tree proprietor) Greg Schlaepfer you don’t need to know how this magic works under the Kontakt hood in order to enjoy this instrument. You’ll only have to master a few simple controls. Once you get the parameters set up to suit your project, you’ll just use your familiar pitch wheel in a very intuitive way and let the scripting do the work. This isn’t to say you’ll never have to edit pitch bend events again, but you won’t have to do it nearly as often.


Using the Pitch Bend Feature

There are six sliders in the User Interface that control how slides work. Sorry, I know I’m using “slide” for two different meanings (“sliders” refers to the UI controls shown below), so I’ll call the Kontakt sliders “controls” to avoid that ambiguity.

The first of the six controls, labeled “Slide Position” is on the General tab.

What this does is set the approximate starting position of the virtual slide. At its default value of 0, you’ll hear more of the higher strings, a brighter tone with longer sustain. Higher numbers simulate playing higher on the neck, with a mellower tone and shorter decay. I tend to use this as a kind of tone control, usually setting it between 0 and 3. In the sample song at the end of this article, it’s at the default position of 0 for maximum sustain.

The other five controls are on the Pitch Bend tab.





Bend Range” works just like the bend range control in any synthesizer, telling the instrument how far to change the pitch when the wheel is at is maximum throw. In the above image, we’re limiting the range to 2 semitones, a good value for typical note-bends such as sliding into a note during a melodic line. It can go all the way up to 12 semitones, a full octave.

I’ve found it useful to automate this parameter so that I can switch to different ranges as the song progresses. Here’s a track (linked at the end of this article) in which I’ve added MIDI automation to switch the bend range from 3 to 12 to 2 to 8 semitones. This makes precise pitch modulation much easier, whether you’re playing it live or drawing it into your DAW’s Piano Roll editor.


Snap to Scale” tells the script how to constrain multiple bent notes to a scale. This addresses the scenario I described earlier, where you want to slide from a major to a minor chord, requiring the root and third to move by different amounts.

Snap to Scale alters the bend range for each note so that they bend by an appropriate amount, as if you had separate pitch wheels for each virtual guitar string. The default setting is “CHR” (“Chromatic”), which means “bend them all the same, like a typical synthesizer”. Other options include major, minor, diminished, M.M (melodic minor) and W.T. (whole tone). In our major-to-minor example, we’d set this to “Minor” to let the instrument know we want to slide up to a minor chord.

Here’s an audio clip that demonstrates the effect of different Snap to Scale options. Keep in mind that it’s the same C-major chord being played six times in a row, pitched up 3 semitones and then back down, just with different Snap to Scale options each time. Most of these would be impossible to play or program with a conventional synthesizer without overlaying multiple parts.

    Snap-to-Scale Options


Snap to Key”, as the name implies, makes sure that at the end of the slide we end up in the proper key. In our C major to D minor example, we’d set this to “C”.

Bend Affect” is not a misspelling of “Effect”. Rather, this control determines which notes in a chord will be affected by the slide. The default is “ALL”, meaning all notes will be pitch-shifted.  But we can use this control to affect slides that normally can’t be done on a normal synthesizer or sample library: sliding just one note of a chord.

Bend Affect choices are ALL (slide all notes), LOW (slide the lowest note only), HIGH (slide the highest note only), FIRST (slide only the first note played) and LAST (slide the last note played).

But what if you want to bend everything EXCEPT the lowest note, or everything EXCEPT the first note in the chord? For that, we’ve got the “Bend Handling” control, a two-position toggle. At the default value of “INCL.” (inclusive), whichever note we described with the Bend Affect slider is bent. If we move that to “EXCL.” (exclusive), everything EXCEPT that note gets bent. Got it? Yeah, it’s a little confusing until you play with it but then it’s pretty obvious.

All of these parameters may be automated, which can make for a more realistic performance.

Here’s a video by Greg that shows how it works:


Although the video demonstrates a different product (OTS Lap Steel) it’s the same controls and scripting as in Slide Acoustic. Master either of them and you’ll know what to do with the other. The Lap Steel is a similar instrument, but with a raunchier, metallic tone. Greg offers both of them together as the “SLIDE Bundle”.


Effects and Vibrato

As you’d expect, there are the usual assortment of effects: EQ, chorus, delay, reverbs, amp sims, compressor, tremolo. I don’t need to explain these to you, as they’re the same built-in Kontakt effects shared by every Kontakt instrument. All except for vibrato; that’s a different animal.

As with most Kontakt instruments, vibrato intensity is controlled by the Mod wheel, and the Vibrato Depth control (on the General tab) determines the Mod wheel’s range. But Slide Acoustic’s vibrato is definitely not the generic vibrato script that’s provided by Native Instruments and used by many Kontakt library developers. Rather, this vibrato script was custom-made for this instrument.

If you imagine playing a guitar with a slide, it’s obvious that vibrato cannot work the same way as it does with finger-fretted strings. Rocking the physical slide doesn’t just alter the string’s pitch, it also excites the string and makes it continue vibrating longer. This makes for a cool effect, especially if you bring the vibrato up at the tail end of a long sustained note; as the note fades away you’ll hear the scraping sound of the slide continuing to vibrate the string. (Listen closely to hear this effect at the very end of the sample song linked below.)

One more comment regarding effects: be sure to try this instrument with either the built-in amp and cabinet selections or with your favorite external amp/cab simulation software such as Guitar Rig, Amplitube or S-Gear. It may seem sacrilegious to amp up an acoustic guitar, but doing so can turn it into a completely new instrument. Listen to the Rolling Stones’ Jumpin’ Jack Flash; there are no electric guitars on that record, only dirtied-up acoustics.

Here’s a sample song I created that uses three Orange Tree instruments. The bass is the OTS Rickenbacker and the main melody is OTS Stratosphere. Skip forward to the last verse at 3:17 to hear the OTS Slide Acoustic (through Guitar Rig). Note the varying slide lengths, using the automation pictured in the earlier screenshot. Although all the guitar parts feature bends and slides, I want to point out that the Stratosphere portion took me the better part of a whole day while the Slide Acoustic bit was done in 30 minutes.




How to Get It

Go to and pick it up for $89 ($129 for the bundle with the Lap Steel). Available only as a download (1.9 GB).

You will need the full version of Kontakt 4 or 5, not the free Kontakt player. There are no special memory requirements, as it’s a relatively lightweight library, about 302 MB loaded. Total disk space needed: 2 GB.



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