I see a few octave pedals mentioned quite a bit here and thought some people might find this useful. I wont go crazy in depth, just some general observations. Please chime in with any additions and fwiw I mostly use active 5 strings and use oct down for single note use and these reviews reflect this. Starting with the ones I have in no real order: Valeton OC10- I havent had a OC2 in over a decade but this reminds me of the Boss, glitchy character and all only smaller. Very well constructed and the easiest to hit on/off switch for a mini pedal. Cheap and easy to get. Cog T16 v2- Sounds as advertised. Loud and full, tracks wonderful, tight and fast. I use one on my guitar board too. The way I have it set it reminds me alot of the Mooer Tender Octaver v1 but louder and punchier. I dont really use the potential OC settings but its tighter than the Valeton when set that way. Mooer Tender Octaver v1- Very clean sounding, tracks great and has decent output. Has that POG vibe. Combined with a Slow Engine it gives a nice bowed upright sound. Ive not tried the v2. Broughton Synth Voice- Probably my fav of the bunch for bass. Tracking is great, sounds is top notch. Clean, fat, warm and smooth. Doesnt fair well with guitar tho. The video on the website sold me on it and is very accurate representation of it. Broughton Broughctave- Kinda raunchy in comparison to the Synth Voice. It cant get quite loud too. Not that I use it much but I like the dirty channel best. I can get a pretty unique sound out of it, hard to describe. I find myself constantly tweaking this one more than any others. Lots of variation but I cant seem to settle on permanent settings. Eventide Pitchfactor- Been my main oct down pedal for a long time(until Synth Voice and T16). No tracking issues, not overly digital sounding imo, has some gritty character. Plus alot of other cool sounds in that box. Kinda big for 1 main effect use but its been on my board forever. DOD Meatbox and Mantic Destiny Hulk- I wouldnt really recommend these for oct down sounds unless you have some sub woofer action happening. If you do, these are room shakers but I find the playability range is kinda narrow and tracking could be more consistant. Again they dont get fully justified imo without a serious sub Ones I no longer have: Bass Whammy- Ive always like the whammy but the size it too much for just using oct down. Plus I always felt like it could have used more output on that setting. MXR Bass Octave Deluxe- Probably the first octave pedal I had specific for bass. Very popular probably for reasons Im sure but Ive was always under whelmed by it. Maybe I need to give it another go or try the Sub Octave or Sub Machine Mutron Octave Divider(70s version)- Loved the sound and function of this one. It would nail that classic funky sound. Tracking was decent but didnt go real low from what I recall. Sounded great with guitar too. The age and size were a deterrent. Looking forward to trying the new mini version. Foxrox Octron 2- Sounded like the Mutron to me but was overkill for my oct down use. I also really prefered this one on guitar than bass. Boss OC2- maybe the most documented so I wont say much and its been a long time since I owned one. I will say that Im very happy that there is now some other offerings that take what I didnt like about it and really improved on it. Id still like to try the 3 Leaf Octabvre but very content with the Cog and Broughton for now. Im sure theres some others worth trying too, feel free to list them up.