Digitech Mosaic

Ok it will not replace a 12 string in a recording environment, but saying that, buried in a mix you really can't tell much difference between a 12 string electric and this .... as long as you don't go too high up the neck.
I also use this on acoustic guitar, where a little subtle use goes a long way. I put a TC spark in front to give it a bit more signal to play with and the results are really nice.
Be warned, this like the Digitech Luxe (one of my favourite pedals) are the 'older' current hungry pedals asking for 300mA, so if you have a 500mA power block it is a greedy little thing, which will starve your other pedals.
For playing live, it really can't be beaten, in terms of not having to lug around another guitar.
The main difference with this and an octaver is that the two top string are unison (+- a few cents for a chorusy feel), so you don't get that toy guitar sound on the high strings. Playing too high up the neck it does get a bit weird where very subtle is better.
All in all a very fun pedal and save a lot of hassle.
Highly recommended

I got this pedal because I wanted to add the 'illusion' of a 12-string in our gigs. I wasn't going for a specific sound - just wanted to add some more options to my pallet. I haven't had a chance to try it in a live setting or even in rehearsal, so this review is about how it sounds on its own and not within a mix or a band (could be amazing, can't say). From my limited experience so far what I can say is that the extreme settings can sound less-than-stellar. If used with moderation, it gives indeed a good 12-string imitation. For me, this means the Tone setting between 9-10 o'clock and the Level between 13-15 o'clock depending on guitar and amp used (Level all the way clockwise can also sound interesting if going for a very pronounced effect). Overall I am quite happy with the sound, I guess in a live/band setting the small reservations that I have would be hidden in the mix.

...and then you'll get a very convincing 12 string sound. The range of adjustments is not huge but that makes sense given the purpose of this pedal. I have owned three 12 strings in my life and I am familiar with the "behavior" of the 12 strings. The light chorus coming from impossible-to-tune 12 strings is there and at lower settings the high E and B strings are unisson like on the real thing. You won't get that from an octaver. Beautiful pedal!
Digitech makes cool stuff. I bought the Freq-out as well and it's equally brillant.

I get all my stuff from Thomann. They are the best!

The first thing I did when I got this item was to check it really was true bypass. I.E. does it need power in the bypass condition. No it does not. Great. I am fed up with op amps labelled as true bypass which my ears tell me is not. This is true bypass. OK so now to does it do what is says on the packet? Yes. In fact I might go a little further. I am crap at playing 12 string, and I hate the faff of tuning. SO I never bother with a real 12 string of any sort when playing out, I am not good enough to play one out to an audience. Now I get the 12 string sound, with clean chords and don't have to change guitar mid gig. Digitech have nailed it with this one. Someone who popped around to our studio, another musician said he could not tell the difference to his ears. Maybe if we had swapped my Guitar for a tuned uo a 12 string we might, but then all 12 strings sound different. Digitech are happy to warrant this for four years and I like the range of mix and tones it offers. We could hear no glitching, which to be honest we were expecting to need to play around, so one more thing not to have to worry about. The power adaptor was supplied with both European and US troucs for the travellers amongst us, shame there wasn't a UK/HongKong one in there as well! Overall very impressed, and it has already claimed it's place on my very limited board. (Tuner is the only other item, we use the other space for transporting things like leads etc to gigs.
I might even try it on acoustic!

this pedal is simply amazing. it's not just another octave generator. what sets them apart from other octave generators is the level and the tone knob so you have total control over the high tone. and it is possibly the best looking pedal in my rig. it really looks like a work of art hence the name Mosaic.
I used to have an EHX micro POG but instead, I decided to separate the high and low octaves to have more natural sounding octaves and more control over each. now I use the tc electronic Sub'n'Up Octaver particularly for octaves below (Sub1 and Sub2) and the Digidesign Mosaic particularly for high octave. if you often switch between low and high octaves during songs, that's perhaps the best way to go. this way you don't have to bend over your pedalboard nor do you have to take your hands off the guitar.
Thomann as always has a wonderful delivery and quality packaging which has become their tradition and good reputation.
cheers