Lips
Start open and neutral for "ah". As you move into the r, they round slightly. The diagram shows the open start.
The American "ar": start on a big open "ah", then glide into the r colour. Two positions, one smooth sound.
Example words: car, start, hard, park, far

Start open and neutral for "ah". As you move into the r, they round slightly. The diagram shows the open start.
Start low and back, as for "ah". Then curl the tip up and back, or bunch the mid-tongue, into the r. The tip never touches the roof of the mouth.
Long. Give the open "ah" its full length before the r colour takes over.
Say "car" slowly. You should hear a clear "ah" that smoothly grows an r colour at the end, with no tap and no gap. If the word ends on plain "ah", the r got dropped.
Dropping the r so "car" becomes "cah", or tapping and trilling the tongue instead of holding the curled shape.
🔊 plays the app's native voice. 🎤 records you so you can play it back next to it. Your recording stays in your browser.