Seven unrelated r/singing threads in twelve months ask the same…
Seven unrelated r/singing threads in twelve months ask the same question — how do you learn a harmony line when there is no teacher — and every answer is 'practise more'. The askers are a mother of four, a community-theatre director and a band's backing singer, and they describe the identical failure in the same words: they drift back onto the melody.
What is the idea?
Pick the song you actually want to sing. Get your own harmony line back as an isolated guide track you can loop — and a practice mirror that marks the exact seconds where your voice collapses back onto the melody.
Why would anyone bother?
The people asking are not musicians shopping for a tool. They are a mum whose four kids harmonise at home and get stuck the moment they leave choir, a theatre director whose alto cannot hold her part, a drummer whose band needs him on backing vocals. What they walk away with is their line — hearable on its own, and correctable.
What is missing today?
Everything that exists is either abstract interval ear-training (Perfect Ear, Functional Ear Trainer) or scoring you against the lead vocal (Smule, Yousician). Nobody hands you a harmony line for the specific song in front of you, and nobody catches the single failure every asker describes: sliding back onto the melody.
What makes this one different?
Do not build a singing app. Build one line for one song: twenty public-domain and standard choral pieces, the third above only, an isolated guide track, and a red mark on the seconds you drifted. Cold start (Chinese): 小红书/B站「和声怎么唱」「合唱 声部 跑调」标签下的评论区，以及合唱团家长群; (English): the seven r/singing harmony threads are already a list of people who have raised their hands, plus community musical-theatre groups and church choirs.
What is the sharpest thing about it?
Producing a part that is not in the recording — a defensible third above this melody, in this key, over these chords — needs chord recognition on arbitrary polyphonic audio plus a singable voice-leading pass. Stem separation and polyphonic transcription only became commodity in the last two years. The 'drifting' detection on top is then just two pitch tracks compared in real time.
What could kill it?
Harmony is not one thing — 'the third above' is frequently the wrong note, and a musically honest line needs the chord, the voicing and the genre. Get it wrong and you have taught someone to sing a wrong note confidently, which is worse than nothing. The audience is enthusiastic but small (these threads run 5–20 points, not thousands), and rights on commercial recordings push anything cloud-side into a licensing problem the on-device version does not have.
Who pays, and for what?
A parent already paying for a child's choir, or an adult amateur already paying for a monthly voice lesson — priced against one lesson.
What is the main risk?
The musical quality of the generated line is the entire product, and a wrong line is worse than silence; rights on commercial recordings push the useful version onto the user's own device.
What did real people actually say?
Verbatim from the public sources linked above, not paraphrased: “Most of the time when I try to it's okay for the first couple notes before I end up drifting to the main melody line or ending up somewhere in the middle (and it sounds and feels awful xP).” — reddit r/singing (18 pts / 23 comments) “feels like no matter what i try i can't pick it up, no tutorials so far have helped and i spent basically a year trying to find the harmony when i was singing along to music and just couldn't get it” — reddit r/singing (23 comments) “there's no easy way to learn harmonies to new songs without that guidance. How do you currently learn harmonies when there's no teacher around? Is there an app for this?” — reddit r/singing — mother of four “I have a cast member (a beautiful alto) who is struggling to hold harmonies when singing with others, and has asked for some resources/tips/etc. Problem is, I don't have the answers!” — reddit r/singing — theatre director (13 pts / 15 comments) “My band NEEDS me to be able to sing for harmonies, but I just cant. What do I even do?” — reddit r/singing “When I hear a melody I can sing harmonic over that one. But when I do the same over a song that already has a singers voice in it I, often sing disharmonious.” — reddit r/singing (8 pts / 9 comments)
How much work is it?
about two months of work
Where does the evidence come from?
https://old.reddit.com/r/singing/search?q=harmony+%22is+there+an+app%22+OR+%22wish+there+was%22&restrict_sr=on&sort=top&t=year https://old.reddit.com/r/guitarlessons+learnart+languagelearning+piano+singing/search?q=%22is+there+an+app%22&restrict_sr=on&sort=top&t=year
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