How DeuxDuel ranks songs

Almost every music chart you have seen measures consumption or spend: streams, radio adds, sales, playlist placement. Those are useful numbers, but none of them answers the question people actually argue about, which is which song is better. A stream count tells you what was convenient to press play on. It does not tell you what someone would choose if both songs were sitting side by side.

DeuxDuel asks that question directly, several thousand times a day.

Step one: the pairwise comparison

Instead of asking you to rate a song out of five — which people do inconsistently, and which drifts over time — DeuxDuel shows you two songs and asks you to pick one. This is a pairwise comparison, and it is a much more reliable instrument than a rating scale for one simple reason: you do not have to hold a standard in your head. You only have to prefer one of two things in front of you.

Each matchup gives you both previews. Tap either side to listen, swipe toward the one you are choosing. That is the entire interaction, and it takes about three seconds.

Step two: turning votes into a rating

A single vote is nearly meaningless. The job of the rating system is to turn a large pile of individually meaningless votes into an ordering that means something.

DeuxDuel uses Glicko, a rating system from the same family as Elo — the maths that ranks chess players. It works on one core idea: who you beat matters as much as how often you win.

• Beat a highly-rated song and your rating moves a long way up.
• Beat an unknown or poorly-rated song and it barely moves at all.
• Lose to a song far below you and you drop hard.

This is why a track cannot climb by farming easy matchups. To reach the top of a DeuxDuel category, a song has to beat other songs that have themselves been winning.

What Glicko adds over plain Elo

Elo gives every song a single number. Glicko gives every song a number and a confidence interval — internally, a rating deviation. A song with four votes has a wide interval: we genuinely do not know where it belongs. A song with four hundred votes has a narrow one.

That second number is what stops the chart from being nonsense in its first week. A brand-new song that wins its first two matchups does not rocket to number one, because the system knows it has almost no evidence. Its rating moves a lot in absolute terms but it stays flagged as provisional until the interval tightens.

Step three: the publication gate

The rating maths is only half of the honesty problem. The other half is deciding when a ranking deserves to be shown to anyone at all.

A DeuxDuel category does not publish a public chart the moment it has data. It publishes when it clears three separate bars: a minimum number of total votes, a minimum number of distinct voters, and a minimum number of appearances per ranked song. A category that has been voted on heavily by three people is not a chart — it is three people's opinion wearing a chart's clothes, and it stays private.

What this means for you as a voter

Your votes do three things at once.

They move the global chart

Every matchup you settle updates both songs' ratings immediately. The rankings you see are the live state of that calculation, not a weekly snapshot.

They build your taste profile

DeuxDuel also tracks where your choices agree with the crowd and where they diverge. The interesting part is usually the divergence — the genre where you reliably back the song almost nobody else does.

They decide what gets ranked at all

Because of the publication gate, voting in a quiet category is disproportionately valuable. A category nobody touches stays unranked forever. This is also why the app runs monthly events: concentrating a month of attention on one lineup is the fastest way to push a category over the bar.

What DeuxDuel is not

It is not a trivia game. There is no correct answer, nothing to guess, and no score for knowing more than someone else. If you have played a guess-the-song app, this is the opposite instrument: it measures preference, not knowledge.

It is also not a streaming service. DeuxDuel plays the 30-second previews that Apple Music makes available to everyone, subscription or not. A subscription only adds the option to save a full song to your library.