Jam with friends

A jam is you and your friends playing piano together over the internet, each at your own keyboard. The delay is around 20ms, thanks to Chordzy's low-latency connection. That is short enough to keep time, so you can play a duet without being in the same place.

Jams need the desktop app on every computer, and each player signs in. One of you presses Host a Jam and gets a short session code. The others type that code into the box next to Join Jam. The share button gives a link instead, which you can copy and send. Opening the link launches Chordzy and joins the session. If the app is not installed, the page points to the download. Hosting a new jam closes the last one you hosted.

The speed comes from what travels. Chordzy does not send your sound. It sends each key press and release, and the other computer plays the note itself. That is less than 0.1% of the data a Zoom call spends on audio. A key press leaves your computer in under 2ms, and the sound starts on the other end in under 5ms. The rest is the distance between you: two people across the country usually hear each other within 20 to 40ms.

The two computers connect directly, the way many online games do. That is also why some home networks get in the way. Plug in an Ethernet cable if you can. Wi-Fi works. A cable gives the lowest latency. Stay off phone data. An LTE connection generally cannot reach another computer directly, however many bars your phone shows. Turn on IPv6 with your internet provider or on your router, if it offers it.

If you still cannot connect, your provider may use CGNAT. Starlink's home and mobile plans do, for example. When the provider does not, a setting on your router is doing the same thing. Turning on UPnP, or forwarding ports 25678 to 25700 to your computer, usually fixes that.

The join screen warns you before any of this bites. It shows a line such as "WiFi is slower than wired" or "Your router may limit connections", and a help button under it. Connecting to real-time jams explains every one of those messages and the router settings to try. If none of it works, tell us what the error said and what internet you are on.