The Ambiguous Guitar Duo

Hybrid musical instruments with an identity crisis.

Remember that song where you couldn’t tell if an instrument is a guitar or a piano?

Neither do I.


But now you will no longer forget. Because now, that song can be yours. Now you can make your own confusing music!

Using the magic of phase alignment, we tried to answer the curious question of what would happen if you align samples grabbed from different instruments. With the outcome of this experiment, you can experience a smooth transition between instrument timbres as you hit the keyboard at different velocities.

Using the excellent samples of FlameStudios, FreePats, Patch Arena and bigcat Instruments, we present this one of a kind amalgamation of five different instruments squashed into a bass and a guitar. Well, sort of. Whatever, the outcome is, it is called the Ambiguous Guitar Duo!

Download the Ambiguous Guitar Duo!


  • The library format is SFZ and has been tested (and developed) with Plogue sforzando. Other compliant SFZ players would also work.
  • The samples themselves are in WAV format.
    • 144MB uncompressed
    • 44.1kHz 16bit
  • There are multiple SFZ files provided
    • Guitar and bass with a piano blended in:
      • ambGuitarPiano.sfz
      • ambBassPiano.sfz
      • ambBassGuitarPiano.sfz: Combined version for 88-key live-playing with the guitar shifted to higher keys. Key-switching controls whether there is more bass or more guitar.
    • Less weirdness without the piano:
      • ambGuitar.sfz
      • ambBass.sfz
      • ambBassGuitar.sfz
    • Lightweight versions of the above sampled in minor-thirds:
      • xxx_lite.sfz
  • A MIDI controller with weighted keys or a MIDI-capable digital piano is recommended for live playing. Otherwise, a bit more bravery might be necessary.
  • Licensing: GNU General Public License version 3 or later, with a special exception.

Live Usage Notes

A proper weighed keyboard is recommended. The SFZ libaries have been tested on a Casio CDP-200R and an Alesis Q88. Mini midi keyboards generally have a different velocity response, hence the velocity triggered sample layer changes might sound too abrupt. It might be necessary to modify the SFZ scripts for convenient playing with such MIDI controllers. Thankfully SFZ scripts are just text files!

KVR Audio Developer Challenge 2018

If you like this sample library, consider voting in the KVR DC18, where you would also find other new and free awesome audio production tools.


Ambigous Guitar Duo is made possible with the kind support of the following sound library developers:

Gary of FlameStudios

FS Seagull Steel String Acoustic Guitar
FS Washburn Acoustic Bass Guitar

Roberto of FreePats

Spanish Classical Guitar
FS Seagull Steel String Acoustic Guitar

Chad of PatchArena

Pizzicato Double Bass

Joe of bigcat Instruments

The City Piano


The Ambiguous Guitar Duo is based on Creative Commons and GPL Licensed instrument samples. Hence, the GNU GPL license is adapated.

Copyright 2008 Gary Campion
Modified 2016 by for the FreePats project.
Modified 2018 by Drew Bañas for Signal Experiments.

These samples are released under the GNU GPL. The source code being the sf2files (of which contain the audio samples and settings).


The exact phrasing of these licensing text might still be modified to reflect the wishes of the sample contributors.

GNU GPL information

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see < >.

As a special exception, if you create a composition which uses these sounds, and mix these sounds or unaltered portions of these sounds into the composition, these sounds do not by themselves cause the entire composition as a whole to be covered by the GNU General Public License. This exception does not however invalidate any other reasons why the composition might be covered by the GNU General Public License.

If you modify these sounds, you may extend this exception to your version of the sounds, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.