Free Beta — no charge, ever, during beta

1,382 tunes. Twelve feels.
A band that hears you.

Jam-a-Lot generates a real-time rhythm section — phrased bass, comping piano, and a feel-aware drummer — over 1,382 open-source standards. It hears you through your mic, follows your dynamics and phrasing, and drives your practice session with zero installs or sample downloads.

The Beta is free and always will be during beta — the whole app, in exchange for telling us what's working and what isn't. No card, no trial clock. Prefer to look around first? Guest mode plays 3 demo tunes with the full band, no sign-up.

The Jam-a-Lot app playing Au Privave: the animated bandstand above a chord chart, with the current bar highlighted and reharmonized chords shown in green.
Play any tune. The band follows the chart bar by bar — and Live Changes reharmonizes as you go.
Jam-a-Lot's full-screen performance view: a large, uncluttered chord chart with the current bar boxed and the transport at the bottom.
Full-screen for the music stand. Just the chart, the bar you're on, and the transport.
The Live Mixer: sound pickers including a tight kick with smoother quiet strokes, levels in decibels, stereo pan positions and mute controls.
A real mixer. Levels in decibels, a sound per instrument, and a pan position that puts each player on the stage.
The Listening Band panel: input, intensity, density and register meters, speaker calibration, and sliders for how strongly the band responds.
The band listens. Meters for what it hears, and sliders for how hard it reacts to you.
The Performance Plan panel: intro, head, solo round, bass solo, piano solo, trading fours, last head and ending, each with a chorus count.
Plan the whole performance. Head, solos, trading fours, out head — or reroll it and see what happens. Written endings close at a quieter energy. Click any displayed intro or ending bar to begin right there.
Why Jam-a-Lot

Built for how musicians actually practice.

No robotic quantized MIDI, no rigid pre-recorded stems, no 90s software bloat. Jam-a-Lot gives you an interactive, humanized rhythm section in your browser, including section-level Salsa bell drive for slow-tempo flexibility and restrained Bossa, Salsa and Bolero fills and endings.

iReal Pro

Quantized MIDI
  • Rigid, robotic MIDI playback with artificial timing and static velocities.
  • No real-time microphone response or listening band capability.
  • Static accompaniment with limited live performance dynamics.

Jamzone / Quartet

Pre-recorded Stems
  • Fixed pre-recorded audio stems — cannot edit charts or insert extra solo choruses.
  • Audio artifacts and pitch-shift distortion when transposing keys.
  • No live feel changes, trading fours, or real-time reharmonization.

Band-in-a-Box

Legacy Desktop App
  • Archaic 90s interface with heavy clutter and visual cognitive overload.
  • Massive multi-gigabyte desktop software installer required.
  • No browser cloud access or live acoustic room mic listening.
Mic interaction

Turn on your mic.
The band starts listening.

Jam-a-Lot subtracts its own speaker sound from your mic per frequency bin, then adapts the band's intensity, phrasing, and voicings to your solo.

01

Dynamic energy tracking

Play softer and the band comes down; build and the band builds with you. Integrated frequency-selective speaker leakage suppression lets you play through room speakers.

  • Live intensity, onset density & register meters
  • Play with headphones or room speakers
02

Phrase-gap answers

Leave a gap at phrase ends and the band responds. Piano comping voicings shift register to match your pitch height and comping density.

  • Onset-based phrase-gap detection
  • Register-aware piano voicings & drum fills
03

Motif catch

Repeat a rhythmic figure twice and the drummer locks on, playing it with you through the section and resolving it cleanly into the section fill.

  • Quantized to the active feel's swing grid
  • Locks on 1-bar or 2-bar repeated figures
04

Section & chorus cues

Section boundaries are announced with jazz setup figures, melodic toms, and downbeat crashes. Chorus arrivals are clearly stated so you never lose your place in the form.

  • Phrase-locked trade re-entries on the "and of 4"
  • Distinct chorus vs section downbeat emphasis
The library

One app, every open source.

Jam-a-Lot aggregates open-source chord collections — a 1,382-tune jazz-standards corpus, academic chord datasets, community lead-sheet archives, and public-domain imports. Search once, play immediately.

Jazz standards

1,382 jazz standards — bebop, modal, swing, ballads, bossa, latin, waltz, and songbook classics.

Pop & rock changes

Open academic chord datasets — practice over familiar progressions and popular tunes.

Lead sheets & scores

Public-domain lead sheets import straight in, with full MusicXML and text chart support.

User Tunes & standards

Paste a text chart with repeat and Coda directions, plus separate forms for solos and the last head. Your saved text keeps its section order and spacing, and written intros and endings play as one-shot sections. Set the tune’s time signature, including 2/4 with a complete Bossa Nova groove. Edit bar by bar with beat-accurate punch figures and one-bar meter changes such as 3/4 inside a 4/4 tune. Edits to catalog standards stay in Jazz Standards; original and explicitly copied songs live in User Tunes.

Direct sharing & cloud sync

Send charts to @handles, share via QR codes or links, and auto-sync your library across all devices.

Shape the band

Static tracks play on loop.
A band responds live.

Generated on the fly bar by bar — giving you real-time control over chorus dynamics, trading, feel switches, and reharmonization while you play.

01

Live dynamics & chorus control

Shape the next chorus without stopping. Double time into the out-head, drop to half-time for the bass solo, or dial drummer intensity (1–5) at phrase boundaries.

  • Next chorus: double time, half time, or feel switch
  • Drummer intensity: 1–5 density profiles on the fly
02

Trade bars with the drummer

Press trade to exchange fours, eights, or full choruses. The drummer solos with comping behind you and hands off with phrase-locked cymbal splashes.

  • Trade 4s / 8s / choruses with phrase alignment
  • Seamless re-entry kicks and downbeat markers
03

Live Changes reharmonization

Phrase-planned Coltrane cycles, Bird Blues, turnaround and bridge families, tritone ii-Vs, secondary dominants, back-door turns, and a major-seventh turnaround — with at most two generated chords per bar above 180 BPM.

  • Substitutions display live on chart & bass line
  • Every generic change proves its written arrival and preserves form timing
  • 100% session-only — original chart stays untouched
  • Chord families (C6 = Cmaj7, Cm7 = Cm11) and So What modal minor voicings
04

12 Feels & instant transposition

Switch feels mid-performance, transpose ±1 semitone instantly, or loop sections until clean. Computed from absolute beat clocks with zero timing drift.

  • Swing, bossa, latin, gypsy jazz, soul-jazz, funk, blues shuffle, rock, EDM...
  • Instant semitone transposition & clean section looping
Core Studio

A complete practice studio.

Everything you need to woodshed a standard in one clean browser tab.

Editable chord chart

In-place editing with root × quality × extension pickers, text mode, stable numbered-ending routes, reharm suggestions, and a roadmap strip.

Generative rhythm section

Seeded walking bass, phrase-aware comping piano, and feel-aware drums that groove deterministically without fixed loops—including eight-bar Bolero piano statements that develop across the chorus.

Live mixer & stage plot

Decibel faders, voice mutes, and per-instrument stereo panning. Mix & EQ Studio adds draggable EQ dots, scroll bandwidth, rotary knobs, a level-matched Linear preset with slope shortcuts (default −5/3), DJ filter, echo, stutter and sweep pads, plus separate bass/drum Instrument FX racks for drive, wah, chorus, phaser and delay, with named presets, one-click reset and compact bypassed racks. A desktop toolbar puts every practice tool at the left edge, with descriptive tooltips and distinct piano-key and EQ icons.

12 Feels & Style Lab

Acoustic jazz kit, Latin percussion, and a groovebox synth. Soul Waltz brings a modern funk groove to 3/4, and Soul 6/8 plays the neo-soul / Afro 6/8 pocket felt in two. Samba brings a real batucada — pandeiro, tamborim, ganzá, agogô and cuíca over a kick surdo — with the samba swingue: the third and fourth sixteenths of every beat land early, at every tempo, with a Swingue knob to set how deep. Tresillo and Bolero modern layer kit drums with hand percussion; Bolero modern brings the standard kit forward, accenting the & of 2 with bass, kick and snare. Build and audition custom accompaniment styles in the lab; Microrhythm combines its plots, supports draggable uncertainty, auto-applies edits, offers a small-kit Minimal groove with coordinated bass and comping, includes an experimental Bossa Nova copy, adds a Traditional base that plays African and Réunion patterns on an approximation of their own ensembles, filters timing patterns for Swing/Samba/Bossa compatibility, places a vertical λ slider beside the first diagram, simulates 1–128 bars (default 16), and places affected players at the bottom, highlights the exact affected players, gives Samba the same whole-band timing scope as Swingue, includes measured Waaju and other four-onset studies, and extrapolates λ beyond A/B on an extended shaded diagram. When the chart and stage scroll out of view, a floating Chord changes panel keeps the stage’s rolling playback chords visible, with Play/Pause and tempo; long charts collapse sections to their first line except the one playing.

Live notation & MusicXML

Generated bass lines render on readable staff notation. Review after Stop, print, or export directly to MusicXML.

Knowledge base & embeds

In-app wiki covering rhythm style structures, plus integrated Spotify and YouTube reference embeds for context. Song Info → Play Video adds supported speed controls with YouTube’s pitch correction, grouped playback controls and A/B phrase loops with an optional local-recording waveform popup (zoom, video offset and click-to-place markers), a draggable trim timeline, editable hundredth-second timestamps and fine nudge controls, saved local markers and a manual BPM calculator using taps or counted A/B spans, with playback-speed correction. Soul 6/8 Brushes combines a bass energy ladder from alternate-bar roots to phrases with late pickups and pauses, soft snare rolls and light shaker motion. Solo Transcription separates piano locally before detecting both hands across the full keyboard, with up to three-minute passages, an isolated piano player and WAV download, Both hands or Melody only staff/PDF views, adjustable downbeat alignment, readable tied notation, direct editing with MuseScore-style keyboard shortcuts, swing notation, requantize, split/join/tie and copy-paste, slowed-down selection loops, MusicXML export, undo/redo, synchronized audition and private study files. Online piano separation requires the local helper. Separate agent-assisted reference groove development uses a local audible review before a new style is authored; see the manual.

Solo Transcription remembers original recordings privately on this device for playback after reopening, and Detect follows the beat in the original recording so barlines and chords keep up with a band that speeds up or slows down. Per-bar Half/Normal/Double corrections fit compressed or held measures in the recording without changing the tune chart.

How it works

Three clicks to a chorus.

Zero install, zero sample downloads. Open a tab and start playing.

  1. 1

    Pick a tune

    3 demo tunes open instantly; 1,379 more unlock with a free Beta account. Color-coded chart renders instantly.

  2. 2

    Set tempo & feel

    Choose a rhythm style, dial tempo, transpose keys, set per-chorus performance plans, and practice ii–V–I cadences, turnarounds, dominant cycles, or Coltrane changes through fixed or random key steps.

  3. 3

    Play & drive the band

    Count in and jam. Adjust chorus dynamics, trade fours, or turn on mic listening live while you play.

Frequently Asked Questions

Everything you need to know.

Is Jam-a-Lot really free?

Yes! During open Beta, the complete app is 100% free in exchange for your feedback. There is no credit card required and no trial timer. Guest mode lets you test 3 tunes with zero sign-up.

Do I need to install software or download samples?

No. Jam-a-Lot is completely browser-native. There are no desktop installers and zero multi-gigabyte sample packs to download. It runs smoothly on any modern desktop or tablet browser.

Can I play through room speakers, or do I need headphones?

Both work! Jam-a-Lot includes frequency-selective band leakage suppression that subtracts the backing band from your mic input in real time. You can play through room speakers or headphones seamlessly.

Can I import, edit, and export chord charts?

Yes. You can edit chord symbols with live validation, paste plain-text lead sheets, sketch original compositions, and export your generated bass lines and chord charts to MusicXML or neutral JSON formats.

Two ways in

Free during Beta.
Free in exchange for feedback.

Jam-a-Lot is in open beta with nothing to pay. All we ask in return is your honest feedback to help us improve the band. Prefer to try it first? Guest mode plays 3 demo tunes with the full band, no sign-up.

Guest

$03 tunes · no sign-up

Hear the band before you decide anything.

Try 3 tunes now
  • ✓ Blues in F, Oleo, Mr. P.C. — full generated band, nothing held back
  • ✓ Every feel, tempo, transposition and mixer control
  • ✓ Live dynamics, trading, Live Changes, the listening band
  • — The other 1,379 tunes are locked
  • — No chart editing, no custom tunes, no imports
  • — Lives in this single browser

Sign up with Google or an email address in fifteen seconds. Jam-a-Lot stores only chord symbols and song form; never melody, never lyrics, never proprietary formats.

Ready to shed?

Pick a tune. Shape the band. Play. Then tell us how it went.

Explore a whole-band rhythm blend

Rhythm Lab → Blend combines compatible native-meter grooves across families, including Funk ↔ Swing. The starting pair follows the chart meter, with compatible partner selection and recovery for saved pairs from another meter. Use the colored Play blend button at the top, choose sources at either end of the balance slider, double-click the balance for a continuous sweep with ¼–16 choruses per transition (default 1), shape bass, drums, comping and timing independently, and use Save blend to name a recipe and Load blend to recall it locally or carry it by JSON. EDM sources select Groovebox Synth for the whole blend. Explicit Phrase fit brings Soul 6/8 ↔ Swing into 4/4 with an onset preview. Electronic ↔ acoustic blending in 4/4 preserves the electronic half-time groove. The “Which rhythms can blend?” guide lists usable partners and explains unavailable combinations. Saved microrhythm and other meter conversions remain unavailable.