Jam: play and record together
Connecting to a Jam
Jam → Join the Jam lists active rooms with address:port in Jamulus format, selectable with the mouse and a Copy button beside it. The list shows engine, status and participants/capacity; Directory is hidden. Use your profile name in the client so the site can recognize the connection.
Record the session
Recording controls are enabled only in the recognized Jam. Only the session creator can stop or restart it and, when connected to the Jam, download its ZIP containing the Reaper project (.rpp) and separate WAV tracks. Administrators can download all recordings. The countdown shows the remaining time; the deadline applies even after closing the browser. Recording includes all participants.
From iReal Pro to the Jam
Backtrack Management → Import from iReal Pro opens the DAW importer. It imports chords and form and generates editable MIDI accompaniment: the project remains the source. Jazz uses walking bass, comping and sampled drums; pop, rock, soul and funk use sounds and arrangements suited to their genre. Provenance credit remains in project data. Managing the Jam library requires an administrator.
Editing and saving
Edit directly reopens the clip source. Harmonic and bass parts from automatic iReal import use Jam Progression, dedicated to this flow and absent from menus: the sequence remains fixed while you can change key, sound, inversions or bass line, BPM and groove. Drums open Drum Licks with kit, pattern and grid restored. Overwrite clip updates the clip. At the top, Personal library and Jam library use Load, Delete and Save; the same name updates, a different unused name creates a copy. Genre, playlist and order are retained in the Jam; edits are heard from the next start.
Playlists and live instruments
Choose the track in the shared popup with search, genre, playlist and a paginated table. BPM, count-in and transport are compact; playback continues with the popup closed. Performance parameters places instruments and control transfer in a row of equal-height cards. Each instrument has a horizontal 0–200% volume above its named mute button: changes affect everyone without restarting. Refresh preserves fader gestures. To transfer control, select another musician; the list excludes the backing client and current user. Preferences are retained and restoration does not trigger actions.
BPM and one or two count-in bars
MIDI project BPM comes from the project and can be changed before Play; Estimate BPM appears only for audio backings. Count-in follows the starting MIDI meter: one or two bars mean 4/8 beats in 4/4, 3/6 in 3/4 and 6/12 in 6/8. The beat unit and section tempos are also respected.
Backing track Master
Whoever starts the backing controls its transport and instruments. The corresponding Jamulus client description shows Master BT while retaining the musician’s name; the popup identifies the Master. If that client disconnects, control passes to another connected, recognized and authorized participant without restarting playback. Unknown or ambiguous connections never inherit control. The original description is restored when playback ends. Jamulus chat announces in English who becomes Master BT, including automatic control handoffs. Chat also announces backing start and stop, naming the Master and song. Manual control transfer never interrupts playback. Start notifications include BPM; instrument mute and unmute are announced in chat.
Chord PDF and song form
Saving to the Jam generates or updates the chord PDF: a bar grid with chords, sections, repeats and endings present in the form, using the DAW Player renderer. Repeats are not invented. The download uses the track name instead of chart.pdf.
Audio preparation and cache
On first start, the server prepares audio from MIDI parts: progress is shown and playback starts only when everything is ready. The cache stores MP3 by track, revision, BPM and instrument and reuses existing results. Editing and saving from the DAW changes the revision and prevents reuse of the old version. The default limit is 1 GB, configurable through JAM_BACKING_CACHE_LIMIT; older generations are removed to make room. Backtrack Management offers manual cleanup. The MIDI project remains editable and the cache stays outside Git.
Audio stability and latency
The Jamulus service gives native audio processes precedence when CPU competes with website jobs. Low-latency mode remains enabled; audio quality and buffer sizes are not reduced. This helps limit processing delays but does not remove network or device delay: use Ethernet, headphones and a client buffer that runs without dropouts. Applying an audio-service update temporarily disconnects the rooms.