[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"blog-post-en-what-key-is-this-progression-actually-in":3,"blog-related-en-what-key-is-this-progression-actually-in":389},{"id":4,"slug":4,"title":5,"description":6,"date":7,"lastUpdated":7,"lastUpdatedKey":8,"lastUpdatedValue":9,"author":10,"tags":11,"coverImage":18,"coverImageAlt":19,"ogImage":18,"series":17,"seriesOrder":20,"readMinutes":21,"path":22,"href":23,"__fallback":24,"body":25,"tocLinks":375},"what-key-is-this-progression-actually-in","What Key Is This Progression Actually In?","Most key finders match scales and give you a confident-looking answer. Fretscape asks what the progression actually suggests - and tells you how sure it is.","2026-06-09","knowledgeBase.relativeTime.daysAgo",11,"Kyle",[12,13,14,15,16,17],"fretscape","guitar","key-detection","music-theory","product-building","how-fretscape-thinks","/images/blog/what-key-is-this-progression-actually-in-hero.jpg","A vintage brass compass resting on aged sheet music, its needle settling toward a marked point, with a faint pencilled question mark nearby",5,4,"/what-key-is-this-progression-actually-in","/blog/what-key-is-this-progression-actually-in",false,{"type":26,"value":27,"toc":372},"minimark",[28,32,35,45,51,54,57,71,76,83,86,93,96,100,103,110,113,117,120,127,142,149,156,162,166,173,175,178,185,192,196,203,210,213,216,220,227,238,241,244,251,261,264,268,271,294,297,304,311,314,324,332,334,338,343,346,350,353,357,364],[29,30,31],"p",{},"I gave a few online key finders the same four chords. Fmaj7. Cmaj7. Am7. Em7.",[29,33,34],{},"They all pointed at C Major. Or C / A minor. Some did it with the kind of confidence that made the answer look settled.",[29,36,37,44],{},[38,39,43],"a",{"href":40,"rel":41},"https://fretscape.com/about",[42],"nofollow","Fretscape"," said something different.",[29,46,47],{},[48,49,50],"em",{},"C Major 34%. E Phrygian 28%. A Minor 27%. F Lydian 11%.",[29,52,53],{},"Plus a warning that the progression strongly suggested multiple possible keys.",[29,55,56],{},"If you read those numbers and think Fretscape sounds less sure of itself than the other tools - you're right. That's the whole point of this post.",[58,59,60],"blockquote",{},[29,61,62,66,67,70],{},[63,64,65],"strong",{},"TL;DR","\nMost key finders match scales. They look at the chords, find the major or minor scale that contains the notes, and return a confident-looking answer. That's a useful first pass, but it's a different question to ",[48,68,69],{},"what key does this progression actually feel like."," Fretscape weighs competing tonal centres, modal readings, and how the progression resolves - and returns calibrated confidence rather than confident-looking match scores. For ambiguous progressions, that means showing the ambiguity instead of pretending it isn't there.",[72,73,75],"h2",{"id":74},"the-progression","The progression",[29,77,78,79,82],{},"Take ",[63,80,81],{},"Fmaj7 → Cmaj7 → Am7 → Em7",".",[29,84,85],{},"The notes across all four chords: C, D, E, F, G, A, B. That's the full C major collection - not a single sharp or flat. Every chord sits diatonically inside it.",[29,87,88,89,92],{},"Most key finders stop there. They return ",[48,90,91],{},"C Major",", often at 100%, and call it done.",[29,94,95],{},"That's the easy answer. It's also incomplete.",[72,97,99],{"id":98},"why-c-major-is-right","Why C Major is right",[29,101,102],{},"In C major, the progression analyses cleanly:",[29,104,105,107],{},[63,106,81],{},[48,108,109],{},"IVmaj7 → Imaj7 → vi7 → iii7",[29,111,112],{},"Every chord belongs to C major. There's no ambiguity at the parent-scale level. So C Major being the strongest candidate is correct.",[72,114,116],{"id":115},"why-c-major-isnt-enough","Why C Major isn't enough",[29,118,119],{},"But here's the thing about progressions - they don't always feel like their parent key.",[29,121,122,123,126],{},"The same four chords sit just as cleanly inside ",[63,124,125],{},"A natural minor",", the relative minor of C. That's two competing tonal centres before we've even left the diatonic frame.",[29,128,129,130,133,134,137,138,141],{},"And if you actually ",[48,131,132],{},"listen"," to the loop - pay attention to where it lands, how it sits - the final ",[63,135,136],{},"Em7"," can feel like home. The opening ",[63,139,140],{},"Fmaj7"," is a semitone above E. That's not a coincidence. It's the defining sound of E Phrygian. The flat-second-degree chord against the tonic.",[29,143,144,145,148],{},"Suddenly the progression has another reading: ",[63,146,147],{},"♭IImaj7 → ♭VImaj7 → iv7 → i7"," in E Phrygian. A coherent modal-minor interpretation. And depending on how the progression is played - held, resolved, looped - that reading can feel more true than the C Major one.",[58,150,151],{},[29,152,153],{},[48,154,155],{},"C Major is the most correct parent-scale answer. E Phrygian might be the more musical \"home\" answer when the loop is actually heard.",[29,157,158,159,161],{},"A key finder that just says ",[48,160,91],{}," isn't wrong. It's just missing what's actually happening.",[72,163,165],{"id":164},"what-fretscape-returns","What Fretscape returns",[29,167,168],{},[169,170],"img",{"alt":171,"src":172},"Fretscape's key detector showing four candidate keys with calibrated confidence and an ambiguity warning","/images/blog/what-key-is-this-progression-actually-in-1.png",[29,174,50],{},[29,176,177],{},"Four serious candidates, none of them dominant. Plus a warning that the progression is genuinely ambiguous.",[29,179,180,181,184],{},"Look at those percentages. C Major is the leader, but only by 6 points over E Phrygian and 7 over A Minor. The system isn't telling you ",[48,182,183],{},"\"definitely C Major.\""," It's telling you the chords have several musically valid readings, ranked by how likely each one is.",[29,186,187,188,191],{},"A simple scale-fit answer can't see this. A tool that grades on chord-tone membership says ",[48,189,190],{},"C Major contains every note, that's 100%, done."," The fact that the same notes also sit inside A minor - and that the loop's actual resolution matters - never enters the calculation.",[72,193,195],{"id":194},"why-the-f-candidate-is-f-lydian","Why the F candidate is F Lydian",[29,197,198,199,202],{},"The F-centred reading at 11% isn't ",[48,200,201],{},"F Major",". Plain F major contains B♭. The progression contains B natural - every Cmaj7 and Em7 puts B in the chord. So an F-centred reading of these four chords isn't F major. It's F Lydian.",[29,204,205,206,209],{},"Fretscape labels the candidate ",[48,207,208],{},"F Lydian",". It's only 11% - well behind the leaders. But the label still has to be right.",[29,211,212],{},"If the whole point of the tool is showing the right kind of uncertainty, the candidates that lose still have to be labelled honestly. F Major would be theory-wrong here. F Lydian isn't.",[29,214,215],{},"Even the 11% gets the right label.",[72,217,219],{"id":218},"what-calibrated-confidence-actually-means","What \"calibrated confidence\" actually means",[29,221,222,223,226],{},"When Fretscape says ",[48,224,225],{},"C Major - 34%",", that's not \"34% of the notes fit C major.\"",[29,228,229,230,233,234,237],{},"It's closer to a real probability. ",[48,231,232],{},"On comparable progressions, when Fretscape gives this level of confidence, the answer is correct about this often."," That's a different number to a chord-tone match ratio. A match ratio is just arithmetic - ",[48,235,236],{},"seven out of nine notes fit, that's 78%."," A calibrated confidence is a claim about how often the system is right.",[29,239,240],{},"For an ambiguous progression like this one, low confidence isn't a weakness. It's the honest answer. A 100% answer here would be suspicious - because the progression genuinely is ambiguous, and the percentages should reflect that.",[29,242,243],{},"That means 34% is not a bad score. It is the system refusing to turn ambiguity into fake certainty.",[58,245,246],{},[29,247,248],{},[48,249,250],{},"A 100% answer isn't always a smarter answer. Sometimes the musical answer is: this progression is genuinely ambiguous.",[29,252,253,254,257,258],{},"That reframes what ",[48,255,256],{},"low confidence"," means in the UI. A scale-matching tool that returns 67% is admitting the chords don't all fit. A calibrated tool that returns 34% is saying ",[48,259,260],{},"here's the most likely reading, but there are real alternatives, and you should know that before you decide what key you're playing in.",[29,262,263],{},"Different number, different meaning.",[72,265,267],{"id":266},"why-this-is-the-same-decision-in-different-forms","Why this is the same decision in different forms",[29,269,270],{},"This is the fifth time I've written one of these posts. It keeps being the same decision in different forms.",[29,272,273,274,278,279,283,284,288,289,293],{},"The ",[38,275,277],{"href":276},"/blog/i-built-a-chord-optimiser-that-proved-me-wrong","Am → F transition story"," - the system understood physical movement better than my intuition did. The ",[38,280,282],{"href":281},"/blog/the-optimiser-that-was-quietly-ignoring-me","progression optimiser bugs"," - the system wasn't respecting user intent. The ",[38,285,287],{"href":286},"/blog/technically-correct-vs-expected","voicing ranking fixes"," - the system wasn't respecting user expectation. The ",[38,290,292],{"href":291},"/blog/the-wrong-name-ranked-first","reverse chord lookup honesty"," - the system was performing knowledge instead of giving it.",[29,295,296],{},"This one - the system knows when it doesn't know.",[29,298,299,300,303],{},"Every time, the same question: ",[48,301,302],{},"what does a guitarist actually want?"," Every time, the same answer: not the impressive-confident-looking maximum. The honest one.",[29,305,306,307,310],{},"A scale-fit tool tells you what your chords look like on paper. A tonal-centre tool tells you what your progression actually sounds like. It's the same reason Fretscape's ",[38,308,309],{"href":291},"reverse chord lookup"," doesn't show every name it can technically justify: membership isn't the same as identification. Those are different questions. Fretscape was built around the second.",[312,313],"hr",{},[58,315,316],{},[29,317,318,321],{},[48,319,320],{},"Most key finders tell you what scale your chords fit.",[48,322,323],{},"Fretscape tells you what key your progression actually suggests - and how sure it is.",[29,325,326,327,331],{},"This is the fifth of five ",[38,328,330],{"href":329},"/blog/how-fretscape-thinks","How Fretscape Thinks"," posts. The other four are linked above.",[312,333],{},[72,335,337],{"id":336},"a-few-questions-this-raises","A few questions this raises",[339,340,342],"h3",{"id":341},"why-is-34-the-top-result","Why is 34% the top result?",[29,344,345],{},"Because the other candidates are also strong. C Major is the strongest parent-scale answer, but E Phrygian is a serious modal reading and A Minor shares the same notes. When four candidates are all musically defensible, no single one earns 70%. The percentage is a probability, not a match score.",[339,347,349],{"id":348},"should-i-trust-a-tool-that-says-its-only-34-sure","Should I trust a tool that says it's only 34% sure?",[29,351,352],{},"More than one that says it's 100% sure of an ambiguous progression. Confidence has to be earned. A tool that hands out high confidence freely is one that hasn't been honest about what it doesn't know. Calibrated low confidence is harder to build than uncalibrated high confidence - and far more useful.",[339,354,356],{"id":355},"what-if-i-just-want-a-single-key-for-songwriting","What if I just want a single key for songwriting?",[29,358,359,360,363],{},"Take the top candidate and run with it. C Major is a perfectly reasonable choice for this progression - the maths backs it, the chords work. But if your loop ",[48,361,362],{},"feels"," like it lands on Em7, you're not wrong, and you don't have to talk yourself out of it. Both readings are real. The post isn't telling you to pick the harder answer; it's telling you the easier answer is one of several, and the system shouldn't be hiding the others.",[29,365,366,367,371],{},"Want to try your own? You can ",[38,368,370],{"href":369},"/key-finder","find the key from a set of chords"," and see the same ranked candidates, confidence and all.",{"title":373,"searchDepth":374,"depth":374,"links":375},"",2,[376,377,378,379,380,381,382,383],{"id":74,"depth":374,"text":75},{"id":98,"depth":374,"text":99},{"id":115,"depth":374,"text":116},{"id":164,"depth":374,"text":165},{"id":194,"depth":374,"text":195},{"id":218,"depth":374,"text":219},{"id":266,"depth":374,"text":267},{"id":336,"depth":374,"text":337,"children":384},[385,387,388],{"id":341,"depth":386,"text":342},3,{"id":348,"depth":386,"text":349},{"id":355,"depth":386,"text":356},[390,404,418],{"id":391,"slug":391,"title":392,"description":393,"date":394,"lastUpdated":395,"lastUpdatedKey":8,"lastUpdatedValue":396,"author":10,"tags":397,"coverImage":400,"coverImageAlt":401,"ogImage":400,"series":17,"seriesOrder":21,"readMinutes":402,"path":403,"href":291,"__fallback":24},"the-wrong-name-ranked-first","The Wrong Name, Ranked First","Hand a reverse chord lookup three notes and it leads with C6(no3) over the obvious Am7 - then warns about its own answer. Lookup isn't the problem. Ranking is.","2026-06-08","2026-06-10",10,[12,13,398,16,399,17],"reverse-chord-lookup","chord-naming","/images/blog/the-wrong-name-ranked-first-hero.jpg","A row of blank kraft-paper tags hanging from twine on wooden pegs against dark rustic wood, one tag embossed with a small acoustic guitar, warm light",6,"/the-wrong-name-ranked-first",{"id":405,"slug":405,"title":406,"description":407,"date":408,"lastUpdated":408,"lastUpdatedKey":8,"lastUpdatedValue":409,"author":10,"tags":410,"coverImage":414,"coverImageAlt":415,"ogImage":414,"series":17,"seriesOrder":386,"readMinutes":416,"path":417,"href":286,"__fallback":24},"technically-correct-vs-expected","Technically Correct Isn't The Same As Expected","I was taking a screenshot of Am7 when I realised my ranking had been getting it wrong for months. The voicings were correct. The order wasn't.","2026-06-07",13,[12,13,411,412,16,413,17],"chord-voicings","ranking","user-expectation","/images/blog/technically-correct-vs-expected-hero.jpg","A small wooden three-tier winners podium on a warm desk, a blue first-place rosette ribbon resting on the second-place step while the tallest top step sits empty, golden light",7,"/technically-correct-vs-expected",{"id":419,"slug":419,"title":420,"description":421,"date":422,"lastUpdated":422,"lastUpdatedKey":423,"lastUpdatedValue":374,"author":10,"tags":424,"coverImage":427,"coverImageAlt":428,"ogImage":427,"series":17,"seriesOrder":374,"readMinutes":402,"path":429,"href":281,"__fallback":24},"the-optimiser-that-was-quietly-ignoring-me","The Optimiser That Was Quietly Ignoring Me","I sat down to take one screenshot for the Play Store. Three hours later I'd fixed three bugs in the optimiser - and was very late for a family day out.","2026-06-06","knowledgeBase.relativeTime.weeksAgo",[12,13,425,16,426,17],"progression-optimiser","user-intent","/images/blog/the-optimiser-that-was-quietly-ignoring-me-hero.jpg","A kraft tag held shut by a small brass padlock among looser tags on warm wood, a faint chalk arrow curving past it rather than stopping at it","/the-optimiser-that-was-quietly-ignoring-me"]