How to Create 12-string Sounds with a 6-string Guitar in Real Time

You can transform the sound of a standard six-string electric guitar into a 12-string’s rich, vibrant tone — in real time. The proof is in the listening, so check out this audio example.




The first part features the guitar’s normal sound. The second part showcases this tip’s transformative effect.

Overview

The process requires three tracks. Fig. 1 is based on Studio One but removes Studio One-specific graphics. By showing only the signal flow, you can adapt the technique to whichever DAW you use.

The Dry Guitar track is the guitar input (or guitar track playback). It has no processing.

One pre-fader send goes to the Octave bus. A pitch shifter transposes the audio up 12 semitones. This produces the sound of the octave-higher strings. However, a physical 12-string doubles the top two strings in unison instead of at an octave. To reduce the octave-higher sound in the higher notes, equalization before and after the pitch-shifter plug-in restricts the frequency response.

Another pre-fader send goes to the Top Strings bus. This bus emulates the doubling of a 12-string’s top two strings by inserting a chorus. A low-cut filter reduces the chorus effect in the low notes. This ensures that the effect is most prominent in the high notes.

Mixing the dry track with the two buses sets the balance of the guitar, the octave higher, and the doubled-string effects.

Figure 1: Signal flow for the 6-to-12-string converter

Choosing a Pitch Shifter

The pitch-shifting effects in most DAWs trade sound quality for real-time operation. They typically require rendering time to improve their fidelity. This precludes real-time playing.

This tip uses the Pitch Shifter plug-in from Kilohearts, which is free when you create an account on their website. Although the plug-in introduces some latency, this is a feature, not a bug. With a Rickenbacker electric 12-string, you hit the octave strings slightly later than the fundamental ones. Coincidentally, the latency gives this effect. The plug-in is basic — all it does is shift pitch. So, the fidelity is decent for a real-time processor. Fig. 2 shows the recommended initial settings.

Figure 2:Recommended settings for the Kilohearts Pitch Shifter

EQ Settings

Fig. 3 shows Pro Tools’ control settings for three EQ3 processors. Controls that aren’t used are either not shown or grayed out. Most DAWs include EQs that can reproduce the following settings:

Pre-Pitch Shifter Filter: Lowpass filter at 2.05kHz, 24dB/octave slope (36 or 48dB/octave preferred). Highpass at 110Hz, 24dB/octave slope.

Post-Pitch Shifter Filter: Lowpass filter at 4.00kHz, 24dB/octave slope (36 or 48dB/octave preferred). Highpass at 110Hz, 24dB/octave slope.

Pre-Chorus Filter:Highpass at 600Hz, minimum 24dB/octave slope (36 or 48dB/octave preferred). Use a parametric stage to add about 3dB of gain at 1.67kHz with a Q around 2. Optional: For a brighter sound, add a high-frequency shelf starting around 2kHz. Boost the shelf by 3 or 4dB.

Figure 3: EQ settings. Pre-Pitch Shifter EQ (top), post-Pitch Shifter EQ (middle), pre-Chorus EQ (bottom).

Tips

Balancing the levels of the three paths is crucial. Start with all their faders down. Set the Dry Guitar track level first. Then, bring up enough of the Octave bus to create the 12-string effect on the lower strings. Finally, bring up the Top Strings path to fill out the instrument.

For the most realistic Top Strings sound, program the chorus to generate only two voices. Use slow modulation without much depth.

This technique sounds best with a guitar’s treble, or bridge, pickup (particularly humbuckers).

Consider adding one more bus and routing the three paths to it. Then, you can insert effects such as reverb or image enhancers that will affect the entire guitar sound. Also, once you have the desired balance, you can change the overall level with one fader.

Studio One and Ableton Live can include the necessary plug-ins on a single track by using an FX Chain or Effect Rack, respectively.

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