Build Quality:4.9 out of 5 stars
Hardware:4.8 out of 5 stars
Electronics:4.8 out of 5 stars
Sound:4.8 out of 5 stars
Value:4.9 out of 5 stars
Average:4.8 out of 5 stars

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  • Great tracking
  • Wide range of sonic possibilities
  • Flexible and versatile


  • Cannot be powered with batteries
  • A bit synthetic

Effects pedals are all about experiences and inspiration for me. They should never be limiting, unless you don’t care about creativity and all that matters for you is technicality. Music is a surreal phenomenon, in my personal opinion, which is why I’m looking for that extra something in my pedals. Sometimes I find it in affordable stompboxes, in other cases – in high-end range. Price doesn’t matter that much, it’s all about the sound and its sparkle. It might be surprising to hear a bassist say such things, but, trust me, this instrument requires a lot of experimentation too. What I’m trying to say is that sometimes we need a pedal that does one thing but succeeds at that, while in other cases we long for a unit that can be used in many different ways. I don’t say this frequently, but you can use an electric guitar pedal with your bass. I know, I know, bass-dedicated units are better, but that doesn’t mean we can’t look out of the box. Today we’re going to discuss Donner Harmonic Square. It offers a lot of versatility in terms of sound and might even have several impressive features. If you are just getting started with the effect either with electric or bass guitar, then this might be the perfect pedal for you. Let’s get started and find out together if you like it or not.


When you see the price tag your instincts might tell you to stay away. Harmonic Square is cheaper than a dinner in a fancy restaurant, which causes mistrust in the majority of cases. However, Donner has already gained its reputation and holds up to the expectations frequently. The pedal we’re discussing is definitely the star of this brand. It is so versatile you might not believe your eyes, and once we move on to the sound section, you’ll notice that diversity translates into tones as well.

This bad boy offers 3 modes of operation. With a twist of a toggle you can alternate between Sharp, Detune and Flat. Each of them delivers a different flavor of octave and lets you explore the potential of the pedal even better. Additionally, Harmonic Square has 7 octave modes i.e. ±2, ±3, ±4, ±5, ±7, 1 octave and 2 octaves. Though some of these options might be too much, especially for your bass, the majority of them are quite usable. Keep in mind that this is a digital pedal, so don’t expect those analog vibes here. It isn’t a bad thing by any means, it’s simply about the preferences. This bad boy is housed in a tiny enclosure that can be mounted even on the most overcrowded pedalboard. Its small footprint makes it really easy to use and carry around. Plus, the body is made out of aluminum alloy which is stable and rugged. As it usually is with such tiny pedals, Harmonic Square can’t be powered by batteries. The only option we have is an adapter, which isn’t a deal-breaker for me (I stick to that method anyway). Clearly, this pedal doesn’t play any games – even though it looks like a toddler’s toy due to its size, it still manages to deliver versatile and powerful performance.


Tiny pedals are usually synonymous with lack of control, but that isn’t the case with Harmonic Square. Its small surface houses three knobs and a toggle, which means you can be in full control of your tone. You can’t tweak it inside out but you can definitely modify all the basic parameters. This is another minor addition that really raises the bar for competitors. I’m sure you won’t have any trouble grasping what is what here, but I still want to discuss available controls briefly.

Wet sets the volume of the affected signal, while Dry does the same thing for your original sound. The most dramatic changes happen when you mess around with the toggle. It enables you to choose between Sharp, Detune and Flat modes and utilize a different amount of pitch shifting each time. The huge encoder in the middle of the pedal makes it possible to select go up or down by 2, 3, 4, 5, and 7 semitones, as well as 1 or 2 octaves. You can activate or turn off the unit with a press of a footswitch – it’s as simple as that. As we’ve seen, adjusting Harmonic Square is a piece of cake.

Donner Digital Octave Sound

Before we start describing the characteristics of the sound, I have several things to say. As I have mentioned above, Harmonic Square can be utilized with guitar and bass equally. It is the combination of pitch shifting and octave, which means that you have to be careful with the adjustments you make. I don’t recommend using 2 octaves with your bass, since it will lose its low-end. For classic octave sounds, you can go for 1 octave, but you can always experiment with other settings and check if they sound better with your instrument. You can choose the degree of detuning with the help of the modes. The tracking is wonderful here – your bass guitar will be reproduced accurately. You won’t lose your low-end, which is one of the things we require from such units. The effect itself is well-defined. Even though it might not be usable in all the settings (it hugely depends on your instrument), it offers a vast array of options.


To sum up everything said above, Donner Harmonic Square is a great affordable option for bassists and guitarists equally. It combines pitch shifting and octave effects, offers 3 modes of operation and 7 variables to choose from. I think you already understand how much versatility you can get out of this device. Its tiny enclosure will be convenient to carry around or mount on the pedalboard. Harmonic Square is for those who don’t stick to one single setting and love to experiment with their pedals. After all, this puppy knows how to bring out the best qualities of your sound. Surprising yet fascinating pedal, indeed! Good luck! 

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