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Thiemo TizianiandClaude Opus 5.5 8133cd0b4b Site 1.1.1: the 3-band waveform in testing on Upcoming
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<a class="brand" href="index.html"><span class="disc" aria-hidden="true"></span><span>CDJ-900NXS Mods</span></a>
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<div class="h">Start</div>
<a href="#install">Install</a>
<a href="#cli">Command line</a>
<a href="#stock">Back to stock</a>
<div class="h">Mods</div>
<a href="#rgb_waveform">rgb_waveform</a>
<a href="#extended_bpm">extended_bpm</a>
<a href="#phasemeter">phasemeter</a>
<a href="#cuecolours">cuecolours</a>
<a href="#hotcuekeys">hotcuekeys</a>
<a href="#beatjump">beatjump</a>
<a href="#ledsaver">ledsaver</a>
<a href="#keynotation">keynotation</a>
<a href="#credit">credit</a>
<div class="h">Hot cue keys</div>
<a href="#hk-mode">The hot key mode</a>
<a href="#hk-load">Loading</a>
<a href="#hk-play">Play a hot cue</a>
<a href="#hk-gate">Gate</a>
<a href="#hk-set">Set a hot cue</a>
<a href="#hk-delete">Delete a hot cue</a>
<a href="#hk-leds">The LEDs</a>
<a href="#hk-limits">Good to know</a>
<div class="h">More</div>
<a href="#status">Status</a>
<a href="#faq">FAQ</a>
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<article class="prose">
<div class="eyebrow">Documentation</div>
<h1>Using the mods</h1>
<p>Everything you need to build the update, put it on your CDJ-900NXS and use each mod. The player must run the official firmware <strong>1.31</strong>; the builder only accepts that update.</p>
<!-- ===================== install ===================== -->
<h2 id="install">Install</h2>
<ol>
<li>Get the official <code>C900NXS.UPD</code> for firmware 1.31 from Pioneer DJ.</li>
<li>Open the <a href="builder.html">builder</a> and choose the file. It checks its SHA-256 and refuses any other file.</li>
<li>Tick the mods. Ticking a mod also ticks what it needs (<code>hotcuekeys</code> needs <code>cuecolours</code>); unticking one unticks what needs it.</li>
<li>Confirm the two points (no liability, code written with Claude Code) and build. Everything happens in your browser: nothing is uploaded, nothing is downloaded.</li>
<li>Download <code>C900NXS.UPD</code>, copy it to the root of a FAT32 USB stick and run the update from the player as you would for an official update.</li>
</ol>
<div class="callout"><strong>What the builder guarantees.</strong> Only the main application is replaced. The boot loader and recovery loader (flash 0x0–0x3FFFF), the S-record header and entry record, and the DRIV and PANL sections are copied from the original byte for byte and checked again on the finished file, which is also unpacked again and compared with the patched application. The patched application is checked against the SHA-256 of the one the Python patcher makes for the same mods, so the file is the same byte for byte. The file is labelled 1.32 so that the player does not skip it as the version it already has; the player still reports 1.31.</div>
<h2 id="cli">Command line</h2>
<p>The Python patcher builds exactly the same file, byte for byte. Tick the mods with the arrow keys and <kbd>Space</kbd>, build with <kbd>Enter</kbd>, accept the disclaimer by typing <code>yes</code>:</p>
<div class="term"><span class="p">$</span> python cdj900nxs_patcher.py C900NXS.UPD</div>
<p>Or name the mods and accept with <code>--accept</code>:</p>
<div class="term"><span class="p">$</span> python cdj900nxs_patcher.py C900NXS.UPD --mods rgb_waveform,extended_bpm,phasemeter,cuecolours,hotcuekeys,ledsaver,keynotation,credit --accept</div>
<h2 id="stock">Back to stock</h2>
<p>Build with no mod ticked in the builder (or <code>--stock</code> with the patcher): the original application, relabelled so the player accepts it. Update as above. Keep this file on a stick before you try any mod.</p>
<!-- ===================== mods ===================== -->
<h2 id="rgb_waveform">rgb_waveform <span class="badge author">arnoldasr</span></h2>
<p>The big waveform in RGB colours from the track's colour waveform data, and the overview's colour table as a red-to-white gradient.</p>
<figure class="shot"><img src="assets/detail-mods.png" alt="RGB detail waveform"><figcaption>RGB detail waveform.</figcaption></figure>
<h2 id="extended_bpm">extended_bpm <span class="badge author">arnoldasr</span></h2>
<p>The BPM to two decimals: the tenths as a small digit above, the hundredths in the place of the stock decimal.</p>
<h2 id="phasemeter">phasemeter <span class="badge author">arnoldasr</span></h2>
<p>A two-line phase meter instead of the four boxes: orange for the master, blue for this deck, each with a marker. UTILITY › SLIP FLASHING becomes <strong>PHASE METER</strong>: ON shows the lines, OFF the stock boxes. The orange marker needs another player as tempo master.</p>
<figure class="shot"><img src="assets/utility-phase.png" alt="UTILITY with PHASE METER"><figcaption>UTILITY › PHASE METER.</figcaption></figure>
<h2 id="cuecolours">cuecolours <span class="badge author">ours</span></h2>
<p>When a track is loaded the player asks its database for the cues. This mod also asks for the extended cue list (the one newer players read from rekordbox's export), which carries the colours and the hot cues.</p>
<ul>
<li><strong>Memory cues</strong> are drawn in the colour set in rekordbox, on the overview and on the big waveform. A memory cue without a colour, or one stored on the player, stays red.</li>
<li><strong>Hot cues A–H</strong> are drawn as small boxes with their letter, in their rekordbox colour.</li>
</ul>
<figure class="shot"><img src="assets/hotcue-overview.png" alt="Overview with coloured memory cues and hot cues A to F"><figcaption>Coloured memory cues and hot cues A–F on the overview.</figcaption></figure>
<!-- ===================== hot cue keys ===================== -->
<h2 id="hotcuekeys">hotcuekeys <span class="badge author">ours</span> <span class="state experimental">experimental</span></h2>
<p>The CDJ-900NXS has no hot cue pads. This mod lends it three: the top three <strong>BEAT DIVIDE</strong> keys left of the jog. It needs <code>cuecolours</code>, which reads the hot cues from your USB.</p>
<figure class="shot"><img src="assets/utility-hotcue.png" alt="UTILITY with HOT CUE KEYS"><figcaption>UTILITY › HOT CUE KEYS.</figcaption></figure>
<h3 id="hk-mode">The hot key mode</h3>
<ol>
<li>Open <strong>UTILITY</strong> (hold <kbd>MENU</kbd>) and set <strong>HOT CUE KEYS</strong> to <strong>ON</strong>. The player remembers it.</li>
<li>Press <kbd>QUANTIZE</kbd> <strong>briefly</strong>: the hot key mode switches on, and a red <strong>HOT KEYS</strong> box appears beside the QUANTIZE label. Press briefly again to switch it off (the box turns grey).</li>
<li><strong>Hold</strong> <kbd>QUANTIZE</kbd> for about a second to switch quantize as usual.</li>
</ol>
<figure class="shot"><img src="assets/display-mods.png" alt="HOT KEYS box beside QUANTIZE"><figcaption>Hot key mode on: the red HOT KEYS box.</figcaption></figure>
<p>In the mode the BEAT DIVIDE keys are hot cues, top to bottom:</p>
<div class="keys">
<div><div class="b">A</div><div class="f">3/4</div></div>
<div><div class="b">B</div><div class="f">1/3</div></div>
<div><div class="b">C</div><div class="f">1/2</div></div>
<div><div class="b">–</div><div class="f">1/4</div></div>
<div><div class="b">–</div><div class="f">1/8</div></div>
</div>
<p>1/4 and 1/8 do nothing in the mode and stay dark: the player has three hot cue buffers, and A–C keep them. With the mode off, or HOT CUE KEYS set to OFF, the keys do what they always did.</p>
<h3 id="hk-load">Loading</h3>
<p>After a track is loaded and the deck stands at its CUE point, hot cues A, B and C are buffered one after another, about a second each, like the CDJ-2000NXS does. Meanwhile:</p>
<ul>
<li>the big waveform stays black and appears once all are ready;</li>
<li><kbd>PLAY</kbd>, <kbd>CUE</kbd> and the hot cue keys are locked, so nothing interrupts the loading;</li>
<li>the key of the hot cue being loaded blinks;</li>
<li>nothing is heard: the output stays silent until the deck stands at its CUE point again.</li>
</ul>
<p>Then the deck stands at its CUE point again, as before, and each of the three starts at once. This happens whether the hot key mode is on or not, as long as HOT CUE KEYS is ON.</p>
<h3 id="hk-play">Play a hot cue</h3>
<p>Press the key <strong>briefly</strong>. The deck jumps to the hot cue and plays — also from a pause, in CDJ and in VINYL mode.</p>
<h3 id="hk-gate">Gate</h3>
<p>Press the key and <strong>keep holding it</strong>. The deck jumps and starts playing at once, exactly as with a short press. When you let go:</p>
<ul>
<li>held <strong>less than 0.5 s</strong>: it simply plays on (a normal hot cue);</li>
<li>held <strong>0.5 s or longer</strong>: it jumps back to the hot cue and stands there, ready to go again.</li>
</ul>
<p>From 0.5 s on the key blinks slowly while you hold it, so you can see the gate is armed.</p>
<h3 id="hk-set">Set a hot cue</h3>
<p>On a key <strong>without</strong> a hot cue (LED off):</p>
<ol>
<li>Pause the deck at the place you want.</li>
<li>Hold the key for <strong>0.8 s</strong>. The hot cue is set there — A in green, B in orange, C in blue — its LED blinks twice and then stays dim, and the box appears on the waveforms.</li>
<li>It is buffered at once, so it starts instantly from the first press. The deck then stands at the new hot cue; PLAY plays from there.</li>
</ol>
<p>Keys that already have a hot cue are not overwritten — delete the old one first.</p>
<h3 id="hk-delete">Delete a hot cue</h3>
<ol>
<li><strong>Hold</strong> <kbd>DELETE</kbd> (beside MEMORY under the screen).</li>
<li>While holding it, <strong>press the hot cue key</strong>. Its LED blinks twice and goes off, and the box disappears from the waveforms. You can delete several keys while holding DELETE.</li>
<li>Let go of DELETE.</li>
</ol>
<div class="callout">While DELETE is held in the hot key mode, the deck does not see it, so no memory cue is lost. If you let go of DELETE <strong>without</strong> pressing a hot cue key, the press is passed on and DELETE deletes the called memory cue as always.</div>
<h3 id="hk-leds">The LEDs</h3>
<p>In the hot key mode the LEDs of 3/4, 1/3 and 1/2 show hot cues A–C; 1/4 and 1/8 are off (SLIP no longer changes them):</p>
<div class="leds">
<span class="led"><i></i> off — no hot cue</span>
<span class="led"><i class="dim"></i> dim — hot cue there</span>
<span class="led"><i class="blink"></i> blinking — pressed, set, deleted or being loaded</span>
<span class="led"><i class="blink"></i> blinking slowly — a gate held (0.5 s or longer)</span>
</div>
<h3 id="hk-limits">Good to know</h3>
<ul>
<li><strong>Set and deleted hot cues are saved on the USB stick</strong>, in the track's rekordbox analysis files with their colours, the same way MEMORY and DELETE keep memory cues; the player shows <em>MEMORY</em> for each. Like MEMORY, this works once the track has settled. Let the last one finish before you load the next track.</li>
<li>A hot cue played from a buffer leaves the <strong>CUE point</strong> where it is. A gate's release stands at the hot cue; PLAY then plays from there.</li>
<li>Hot cues D–H from rekordbox are shown on the waveforms but have no key.</li>
<li>No slip hot cues yet: with SLIP on, a hot cue plays as without SLIP.</li>
</ul>
<h2 id="beatjump">beatjump <span class="badge author">ours</span> <span class="state experimental">experimental</span></h2>
<p>The TRACK SEARCH keys ◀◀ / ▶▶ jump along the track's beat grid instead of changing the track. How far is chosen in UTILITY › <strong>BEAT JUMP</strong> (where SCREEN SAVER was): OFF, 1, 2, 4 or 8 beats; 4 until you choose, and your choice stays when the player is switched off.</p>
<ul>
<li>The jump is exactly that many grid beats, so with 4 or 8 the phase meter shows the same place in the bar after the jump; with 1 or 2 the beats still line up, the bar moves on by one or two beats.</li>
<li>Playing, it is made at once in the audio the player has already decoded: no gap, no pre-roll. Paused or at the cue it moves the deck there; PLAY plays on from it.</li>
<li>The player always keeps 10 s of decoded audio ahead; a press that would leave less (very fast clicks with 8 beats) is ignored and the next one counts again. Nothing is put off, so the player never runs dry (no EMERGENCY LOOP).</li>
<li>It needs <code>hotcuekeys</code> (its engine makes the jumps) and <code>cuecolours</code>; the builder ticks them for you.</li>
</ul>
<h2 id="ledsaver">ledsaver <span class="badge author">ours</span></h2>
<p>UTILITY › <strong>LED ANIMATION</strong> (the last item) is <strong>ON</strong> from the first start; set it to OFF to switch it off (the player keeps the choice). When the player's own screen saver dims the display (5 minutes without a track loaded, or 100 minutes paused or at the cue), the LEDs play a loop of about four and a half seconds:</p>
<ul>
<li>the BEAT DIVIDE keys fade in a wave from top to bottom and back up,</li>
<li>SYNC and MASTER, MASTER TEMPO and DISC EJECT fade in and out against each other,</li>
<li>CUE, PLAY, REV, SLIP, the SLIP LOOP bar and RELOOP/EXIT light one after another,</li>
<li>the jog's three rings light in turn: inner, middle, outer, middle, inner …</li>
</ul>
<p>Any key ends it, as it ends the screen saver.</p>
<h2 id="keynotation">keynotation <span class="badge author">ours</span> <span class="state experimental">experimental</span></h2>
<p>rekordbox writes each track's key as text, in whatever notation was set in its preferences when the stick was exported: <em>4A</em>, <em>9m</em> or <em>Fm</em> for the same key. This mod shows every key in one notation of your choice, UTILITY › <strong>KEY NOTATION</strong> (the last item):</p>
<ul>
<li><strong>CAMELOT</strong> (default) — 1A–12A minor, 1B–12B major, as on the Camelot wheel;</li>
<li><strong>OPEN KEY</strong> — 1m–12m minor, 1d–12d major (8A = 1m = Am);</li>
<li><strong>CLASSIC</strong> — Am, F#m, Db … as rekordbox writes them;</li>
<li><strong>OFF</strong> — the key as exported.</li>
</ul>
<p>The player converts with a table of all spellings, sharps and flats included (G#m, D#m, A#, Gbm …). It works on the main screen, in INFO and in BROWSE › KEY (the key list and its compatible-key groups such as “1A, 1B, 12A, 2A”); a new choice shows from the next track loaded.</p>
<p>Each key is drawn in the colour of its place on the Camelot wheel (8A pink, 5A orange, 4A yellow …), in all three notations; with OFF it stays white. A highlighted row keeps its black text, and the letters you type in SEARCH are left as they are. The player's text colour is set per text box, so the mod sets it for a key's box just before the player draws it.</p>
<figure class="shot"><img src="assets/key-colour.png" alt="Key 5A in orange"><figcaption>5A in its wheel colour.</figcaption></figure>
<figure class="shot"><img src="assets/utility-key.png" alt="UTILITY with KEY NOTATION"><figcaption>UTILITY › KEY NOTATION.</figcaption></figure>
<h2 id="credit">credit <span class="badge author">ours</span></h2>
<p>The boot screen says <em>Pionaarr Mods 1.0</em> where it said <em>Ver 1.31</em>. Ticked at the start; untick it to keep the stock text. UTILITY and the LINK screen still show the real version, 1.31.</p>
<figure class="shot"><img src="assets/boot-mods.png" alt="Boot screen with Pionaarr Mods 1.0"><figcaption>The boot screen.</figcaption></figure>
<p>Quick search, USB auto load, a reversed phase meter, stems and a 3-band waveform are in the works: see <a href="upcoming.html">Upcoming</a>.</p>
<!-- ===================== status ===================== -->
<h2 id="status">Status</h2>
<div class="table-wrap">
<table>
<thead><tr><th>Mod</th><th>By</th><th>Status</th><th>Player</th></tr></thead>
<tbody>
<tr><td><code>rgb_waveform</code></td><td>arnoldasr</td><td><span class="state stable">stable</span></td><td><span class="player">ran on a player</span></td></tr>
<tr><td><code>extended_bpm</code></td><td>arnoldasr</td><td><span class="state stable">stable</span></td><td><span class="player">ran on a player</span></td></tr>
<tr><td><code>phasemeter</code></td><td>arnoldasr</td><td><span class="state stable">stable</span></td><td><span class="player">ran on a player</span></td></tr>
<tr><td><code>cuecolours</code></td><td>ours</td><td><span class="state stable">stable</span></td><td><span class="player">ran on a player</span></td></tr>
<tr><td><code>hotcuekeys</code></td><td>ours</td><td><span class="state experimental">experimental</span></td><td><span class="player">ran on a player</span></td></tr>
<tr><td><code>beatjump</code></td><td>ours</td><td><span class="state experimental">experimental</span></td><td><span class="player">ran on a player</span></td></tr>
<tr><td><code>ledsaver</code></td><td>ours</td><td><span class="state stable">stable</span></td><td><span class="player">ran on a player</span></td></tr>
<tr><td><code>keynotation</code></td><td>ours</td><td><span class="state experimental">experimental</span></td><td><span class="player no">emulator only</span></td></tr>
<tr><td><code>credit</code></td><td>ours</td><td><span class="state stable">stable</span></td><td><span class="player">ran on a player</span></td></tr>
</tbody>
</table>
</div>
<h2 id="faq">FAQ</h2>
<h3>Does this touch the boot loader?</h3>
<p>No. The builder copies the boot loader and recovery loader from the official file byte for byte and checks them again before you can download it. Only the main application changes.</p>
<h3>Is my firmware uploaded anywhere?</h3>
<p>No. The builder runs entirely in your browser; everything it needs comes with the page.</p>
<h3>Can I go back?</h3>
<p>Yes, build with no mod ticked (or <code>--stock</code>) and run the update. Keep that file ready before flashing mods.</p>
<h3>Do I need rekordbox?</h3>
<p>Cue colours and hot cues come from a USB stick exported with rekordbox. Without them the mods show what the stock player shows.</p>
<h3>Why is the version still 1.31?</h3>
<p>The update file says 1.32 so the player installs it; the application inside still reports 1.31 (in UTILITY and on the LINK screen). Only the boot screen says <em>Pionaarr Mods 1.0</em> instead of <em>Ver 1.31</em>.</p>
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<div class="ai"><span class="dot"></span>Made with Claude Code · Claude Opus 5.5</div>
<p>This website, the builder, the mods <code>cuecolours</code>, <code>hotcuekeys</code>, <code>ledsaver</code>, <code>keynotation</code> and <code>credit</code>, and the patcher were developed with Claude Code (Anthropic's AI coding assistant, model Claude Opus 5.5), by reverse engineering the firmware in an emulator. The mods <code>rgb_waveform</code>, <code>extended_bpm</code> and <code>phasemeter</code> are by <a href="https://github.com/arnoldasr/cdj900nxs">arnoldasr</a>.</p>
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<h4>Disclaimer</h4>
<p>Unofficial. Not affiliated with or endorsed by Pioneer DJ or AlphaTheta; CDJ and rekordbox are their trademarks. Flashing modified firmware can leave your player unusable. Everything here is provided as is, without warranty, and used at your own risk.</p>
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