A jam is you and a friend playing piano together over the internet, each at your own keyboard. The delay is around 20ms, which is short enough to keep time, so a duet works from opposite ends of the country. Jams need the [desktop app](/install) on every computer, and each player signs in.

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, so what you hear is mostly the distance between you: usually 20 to 40ms across the country.

The two computers talk directly, the way many online games do, using UDP packets. Browsers do not do UDP, which is why a jam is the one part of Chordzy the web version cannot run.


## Hosting a jam

One player hosts, and everyone else joins that player. Press **Host a Jam**. Chordzy answers with a short session code and a share button that copies a link like `chordzy.com/jam/join/abcd1234`.

Send whichever is easier. The code goes in a chat message; the link opens Chordzy by itself.

Hosting a new jam closes the last one you hosted, so the code you sent yesterday is dead. Send the new one.

A web cam is optional. The desktop app can carry video alongside the notes, and [web cams](/help/hardware/web-cams.md) says which ones it sees.


## Joining a jam

Type the host's code into the box next to **Join Jam**, or open the link they sent. The link launches Chordzy and joins the session for you. On a computer without the app, it opens a page that points at the download instead.

Sign in first. A jam lists everyone in it by name, with the ping between you and them in milliseconds, and a volume slider for each player's sound.

Your MIDI keyboard plays as it always does. The other computers turn the notes you send into sound with their own synthesizer, which is what keeps a jam small enough to arrive in time.


## When a jam will not connect

The join screen warns you before the network does. It shows a line such as **WiFi is slower than wired**, **Your router may limit connections** or **Cellular data may not work**, with a **Learn More (Get Help)** button under it. [Connecting to real-time jams](/help/jams/connections.md) explains every one of those messages and the router settings to try.

Most of it comes down to the network you are on. Plug in an Ethernet cable if you can; Wi-Fi works, and a cable is faster. Stay off phone data, because an LTE connection generally cannot reach another computer directly, however many bars it shows. Turn on IPv6 with your internet provider or on your router, if either offers it.

If a jam still will not connect, your provider may use CGNAT. Starlink's home and mobile plans do, and its business plan does not. When the provider is clean, a setting on your router is doing the same thing, and turning on UPnP or forwarding ports 25678 to 25700 to your computer usually clears it.

Still stuck? [Tell us](/contact) what the message said and what kind of internet you are on.