DJ tools, built on real data.

Everything in this group runs on the same engine as the app: a six-dimension read of how two tracks behave together — harmonic, rhythmic, energy, groove, mood and vocal — rather than a key match with a tempo check bolted on. That is why the answers sometimes disagree with the wheel. Two tracks in compatible keys can still fight over the same midrange, and the score says so.

Reach for Score My Transition when you already have the pair and want a verdict on it. Reach for the Harmonic Path Finder when the verdict is bad and you need what goes between them — it is the only one here that answers with a sequence rather than a number. Reach for the Mashup Finder when you have one track and want the shortlist. The Energy Arc Planner works a level up — it is about the shape of the whole set rather than any single join, and it is the one to open when a set is technically clean and still flat. The Set Length Calculator is the least glamorous and probably the most used: how many tracks fill ninety minutes, at your tempo, with your average track length.

One of them does listen to your files. The Key & BPM Finder decodes whatever you drop and reads the tempo and key off the audio itself, in your browser — which is the answer for a white label, an unreleased dub or anything ripped without tags. The rest work over tracks we have already analysed, and that is the honest limit on them.

These answer questions about a file rather than about music. Reach for the LUFS Meter when you want to know how loud something is in the terms a platform actually uses, and what each of them will do to it — a club master and a streaming master are the same file, and the only difference is that one place turns it down. Reach for the Audio Quality Checker when you do not trust a download: it reads the frequency cliff that exposes an MP3 wearing a FLAC extension, and it checks the thing that is invisible on headphones and decisive on a rig, which is what your low end does when the system sums it to mono.

Both are unusual among our tools in making no network request at all. The chemistry tools have to ask the catalog something; these do not, because every number they print comes out of your own samples. Open the network panel and watch it stay empty — that is a claim you can check rather than trust.

They also both publish what they were measured against. The meter agrees with the reference implementation that commercial loudness plugins are built on to within a hundredth of a unit, and the quality checker's cutoff detection was calibrated on files whose bitrate we chose. A tool that tells you your master is wrong should be able to show its working.

These seven do something to a file rather than measure one, and they share a rule that almost nothing else in this category follows: every operation reports what it changed. By how many decibels, how much was cut off each end, how far off a bar the loop is, what the mono sum cost. A tool that quietly alters a file and hands it back is the reason DJs do not trust these things, and the report is the fix.

The Normalizer is the one to reach for first, and it targets loudness rather than peak — two tracks both peaking at 0 dB can be eight decibels apart to the ear, which is the entire problem it is supposed to solve. The Fade tool sets its lengths in bars, because a fade that does not land on a phrase boundary is one you can hear being wrong. The Looper snaps to the grid and tells you the drift in milliseconds when it cannot, since a loop forty milliseconds off a bar is a whole beat out after twenty-five repeats. The Silence Remover exists for a reason that is not tidiness: leading silence is what makes the same track get a different cue point on every import.

They all write WAV or AIFF and nothing else, which is a deliberate limit. Every one of these takes a file you already own and hands it back changed, and routing that through a lossy encoder would be a second generation of loss caused by a tool that was meant to be helping. Both formats are lossless, both play on every CDJ, and AIFF is the one Rekordbox analyses fastest. Make a smaller file at the end of your chain rather than in the middle of it.

These five deal with the part of DJing that is not mixing: the couple of hundred files on the drive and the metadata that decides whether any of it is findable at three in the morning. Start with the USB Checker on the day of a gig — it opens the rekordbox database that is actually on the stick and checks every track against the files that are actually there, which catches the copied-not-exported stick, the track that will show an exclamation mark, and the file the venue's player will not read. Reach for the Playlist Converter when something needs to get into Rekordbox and Rekordbox will only take its own XML. Reach for the Serato Crate Reader when the thing you need to move is a crate — and it is worth reading that page even if you do not convert anything, because a .crate holds file paths and nothing else, which is the reason every other crate viewer shows you filenames.

The Tag Editor is the one that touches the actual files, and it has a rule the category mostly ignores: it never re-encodes. The audio frames are copied byte for byte and only the container around them is rewritten, which was checked against an independent decoder on eight different file layouts. It also listens to the track, so a folder of white labels with no tags at all can be given its real keys and tempos without opening anything else.

The Tracklist Maker is the odd one out and the most used. It exists for one piece of arithmetic everyone gets wrong: a set is shorter than the sum of its tracks, because every blend overlaps two of them, and a timestamp list built by adding lengths is minutes out by the end.

Harmonic mixing is one idea and five different questions, which is why this is five tools instead of one. The Camelot Wheel is the visual: where you are, and everything one safe step away. The Harmonic Mixing Chart is the same relationships as a sortable table, plus how much material each move actually reaches — the part no other chart publishes. Key Compatibility answers a single pairwise question when you already know both keys. The Key Converter is pure notation: Camelot to Open Key to the musical name, in both directions.

The Cheat Sheet and the SVG pack exist because the wheel is something you want on a laptop lid or a booth wall, not in a browser tab. Both are free and neither needs an account.

A warning worth repeating on every one of them: key detection disagrees between engines. Rekordbox, Mixed In Key, Serato and our own analyser will not always give you the same answer on the same file, and the disagreement is largest on tracks with a modal or ambiguous tonal centre. Treat a key tag as strong evidence, not as a fact, and trust your ears over any of us on the borderline cases.

These are the calculations you do in your head a hundred times a night, done properly. Beats to Time converts bars to seconds and back, which is what you actually need when you are setting a cue point or working out whether a 32-bar intro will cover the outro you have running. BPM to Milliseconds is the delay and reverb one — the number a time-based effect wants if it is going to land on the grid instead of near it.

Milliseconds to BPM is the inverse of the delay one and a different job entirely — you have a number off a loop or somebody else's pedal and no idea what tempo it belongs to, and the answer depends entirely on what you think you measured. The Semitone Calculator sits beside it for the pitch side of the same question. Half-Time / Double-Time is the tool that stops the most common mistake in the list. Drum and bass at 174 and hip-hop at 87 are the same pulse, and a lot of software stores one of them as the other; the tool shows both sides of the octave with how much material sits on each. Pitch and Tempo answers the range question — what a CDJ's default range actually buys you in tracks, which is a very different number at 128 than at 140. And the BPM Tapper is there for the track that has no tag at all.

All of them are arithmetic, so any of them could be built in an afternoon. Where we add something is the last line of each: not just the conversion, but how many tracks in the catalog sit at that tempo.

The tempo tools above are arithmetic: give them a number and they give you another number. These three want the file. That is the whole difference, and it matters because the hard part of phrasing has never been the multiplication — it is knowing where bar one of this particular record is, which no calculator can tell you and which is wrong often enough that every one of these ships with a way to correct it by hand.

The Phrase Counter is the one to open first. It finds the first downbeat, draws every 8, 16 or 32-bar boundary over the structure it detected, and then plays the record back with the count running so you can check it by ear instead of trusting it. The Cue Point Calculator answers the question a DJ actually asks, which is never "where is the drop" — it is "where does the cue go so the drop lands thirty-two bars after I press play" — and then writes the answer into a Rekordbox XML with a real beat grid, so the cues land on the track rather than staying on a web page. The Transition Timer takes two records and plans the join between them: when to press play, where the incoming drop arrives in the outgoing track, and how many bars an unmatched tempo survives.

The DJ Metronome and the Beatmatch Trainer are the two without a file. Where the others read a record, these make the sound. The metronome counts bars and phrases rather than beats, on a pitch fader rather than a number box, with a click that can take itself away for eight bars to find out whether you were counting or following along. The trainer runs two loops against each other, deals yours at the wrong tempo and in the wrong place, and then refuses to show you a meter — you fix it by ear and it tells you afterwards how many bars the mix would have survived. Everything here runs in the browser tab: no upload, no account, no network request carrying your audio.

Name generators are usually a random-word slot machine. These are not: they are prompted with electronic-music context, so what comes back reads like something already on a line-up rather than two dictionary words stapled together. Pick the genre and the feel first — the output changes substantially, and a hard techno alias and an afro house alias should not sound alike.

The DJ, producer and duo generators differ in more than the label. A duo name has to survive being said out loud by a promoter, a producer alias has to survive being a label's artist page, and a DJ name has to survive a room shouting it. The Bio Generator is the one people underrate — a booking email, an EPK and a Beatport artist page all want the same 80 words, and writing those about yourself is genuinely hard.

Nothing here checks availability. Before you commit to a name, search it on Beatport, Instagram, SoundCloud and the domain registrar yourself. We can tell you it sounds right; we cannot tell you it is free.

Genre tags get treated as marketing, but for a working DJ they are a compression of production convention: tempo, arrangement length, how the low end is mixed, where the breakdown lands. Both tools here take that seriously. The EDM Genre BPM Chart is the flat view — every genre once, sortable, with the conventional range next to the median we actually measure. The Genre Tree is the hierarchy — what descends from what, which is what tells you why two genres blend.

The measured column is where these stop being a copy of any other genre list. Conventional ranges are quoted, not verified, and most of them hold up; the interesting ones are the genres that do not, and every one of those misses in the same direction. The chart names them.

Both are also honest about their gaps. A genre only gets a measured number when the catalog can separate it, and several real scenes share a tag with a bigger neighbour. Where that happens the tools say so instead of printing a zero.

These are the only tools here that have nothing to do with audio, and they exist because the paperwork side of DJing is served by Word files on blogs. A Word file cannot subtract the deposit a promoter already paid, cannot know that a booking in Berlin will have 15.825% withheld before the money reaches you, and cannot turn “50% if cancelled within 30 days” into the date and the amount it actually means. All three of those are arithmetic, and arithmetic is the part a template gets wrong.

They are built as a set rather than as four downloads. Your name, address, bank details and the booking itself are entered once and held in your own browser, so the fee on the contract is the fee on the invoice and the set time on the rider is the set time you agreed. Nothing is uploaded and there is no account — which also means clearing your browser data clears them, so save the PDFs you care about.

Reach for the contract when the booking is confirmed, the rider at the same time so production has it early, the invoice after you have played, and the press kit before any of it. Each one prints through your browser, so the PDF has selectable text and comes out on your own paper size.

These are the interactive parts of the longer articles, pulled out so you can use them without reading the whole piece. The Vocal Compatibility Guide is for the specific problem of two vocals colliding — which combinations survive a blend, and what to do with the ones that do not when the mix is already committed. The Key Mood Explorer is the opposite kind of question: not whether two keys fit, but what a key feels like, which is how most people actually choose a closing track.

They live inside their articles rather than on their own pages on purpose. Neither is much use without the surrounding explanation, and a tool that needs a paragraph to be understood should be next to that paragraph.