Is 'sit' vs 'seat' really just about how long I hold the vowel?

No — length is real and measurable, but it's not the whole contrast, and treating it as the whole contrast is why "just say it longer" advice often doesn't fix the pair.

30-second version: /ɪ/ (sit) and /iː/ (seat) differ in three ways at once: duration (short vs long), tongue height (/ɪ/ is slightly lower and more relaxed), and tenseness (/iː/ is produced with more muscular tension and lip spreading). Stretching /ɪ/ out longer without changing tongue position produces a long, wrong vowel — recognizably different from both targets, and often still scored as a miss, because duration alone doesn't move the acoustic evidence to where /iː/ actually lives.

Why "hold it longer" isn't enough

Linguists call this a tense/lax distinction, and it's genuinely a three-part difference, not a one-dimensional slider from short to long. /iː/ is a tense vowel: the tongue muscles work harder, the tongue sits higher and further forward, and the lips spread more, closer to the shape of a smile. /ɪ/ is lax: everything is a little lower, a little more relaxed, and shorter as a natural consequence of that relaxation — the shortness isn't an arbitrary rule, it follows from the more relaxed articulation.

This is why simply holding "sit" longer produces something a native listener still hears as wrong, or at best ambiguous — the length changed but the tongue never moved to where /iː/ actually sits. It's also why many learners report that they "already tried making it longer" and it didn't help: they were right that it didn't help, because length alone was never the fix.

How sayit measures the difference

sayit's acoustic model reads the full formant pattern for each vowel — the resonance frequencies that come from tongue height, tongue position, and lip shape together — not just how long the sound lasted. That means a stretched-out /ɪ/ that never became genuinely tense and high still registers as /ɪ/, or as an ambiguous vowel between the two targets, rather than getting credited as /iː/ just because it ran long. The alignment reports whichever target phone the acoustic evidence actually matches, so the feedback stays honest about what changed and what didn't.

What the fix looks like

Work all three dimensions together rather than one at a time:

• For /iː/: spread the lips noticeably (closer to a smile than you'd expect), lift the tongue higher and more forward, and let the length follow naturally from the tension — don't force the length independently of the tongue position.
• For /ɪ/: relax the jaw and tongue, keep the sound short and a little lower than /iː/, and resist the urge to spread the lips the way you would for /iː/.

A useful check: say /iː/ and feel whether your cheek muscles are doing real work (they should be, from the lip spreading). If the sound is effortless, it's probably drifted toward /ɪ/ regardless of how long you held it.

Drill it

Sit vs seat is the direct pair. Related pairs using the same contrast: bit vs beat, fill vs feel, and live vs leave — running through a few reinforces the contrast faster than drilling one pair alone, since your ear and mouth both need repeated exposure to the pattern, not just one word pair.

Record: "Please sit in the seat by the window." Both vowels two words apart, which makes a merge audible on playback even before you check the score.

The /phonemes/short-i and /phonemes/long-e pages have the full articulation steps for each sound individually.

How do I know it's improving?

Check whether the two words in the drill sentence get consistently different verdicts across several takes, not just one. A pair that's still merging often flips — sometimes both score fine, sometimes both get flagged — because the contrast hasn't stabilized yet; consistent, correct differentiation across takes on different days is the actual target.

Try it

Open sayit free — no install, no card — and record the drill sentence. If "sit" and "seat" get the same verdict, listen back specifically for lip spreading and tongue height, not just how long you held either vowel.