The OP-Z is a tiny musical instrument designed by Teenage Engineering. It fits in a pocket, runs on battery or USB, and offers many functionalities such as sequencing, sound synthesis, sampling, MIDI over USB and Bluetooth or DMX lights controls. New features can also be added with expansion modules.
Unlike the OP-1, its famed predecessor, the OP-Z is screenless. However, with the official app, you can use an Apple or an Android device to display additional information and precise values for the numerous parameters. This is especially useful to learn how everything works, but not mandatory.
Besides this, the app provides a few handy options and shortcuts, and even a way to sync your photo library or Unity scenes to your tracks. More settings can be tweaked by editing a text file in USB mode, which is also used for transferring samples, short loops exports and backups, and firmware updates.
Classic sequencing is indeed possible, but the workflow is geared towards live performance and experimentation. The sequencer includes various ways of adding randomness and conditional notes and effects. This makes the OP-Z a lovely device to create complex beats and evolving soundscapes.
I love this little machine. It's incredibly refreshing compared to a traditional DAW. The interface may seem cryptic at first, but the workflow is in fact rather intuitive, and new ideas will quickly take shape once you've understood the basics. You can use it as a musical sketchpad, as a controller, or even as a standalone production solution if you're in a minimalist mood.
This being said, I wouldn't recommend it to complete electronic music beginners. It packs tons of features, so it can be a bit overwhelming. There's also the matter of build quality. Personally, I have no issue with mine, but there are reports of bent units with encoders popping out.
Just don't expect a highly reliable piece of gear, but a playful device designed for fun and audiovisual exploration. Yes, it can crash. I don't care, it's so much fun, so inspiring, and so great to make beats anywhere, it doesn't matter.
There's nothing similar on the market, except maybe other TE products like Pocket Operators and the OP-1. I've seen people saying it's an overpriced toy. To me, it definitely isn't. It's not for everyone, but it perfectly suits my needs.
The official guide is quite complete, and you can find useful cheat sheets and video tutorials online, but for an in-depth manual, I highly recommend the OP-Z Notebook by Synthdawg.