The starting point for our discussion of rhotics is the voiced alveolar approximant [ɹ]. This is the commonest variety of rhotic in English, and is used in Britain, Ireland, North America and most parts of the Southern Hemisphere. To produce this sound, the tongue tip or blade is raised up towards the alveolar ridge in a stricture of open approximation, the velum is raised and the vocal folds vibrate.

However, this is a simplified description. [ɹ] is frequently accompanied by other articulations. If you compare ‘red’ and ‘led’ and watch your lips, you may well see that for ‘red’ there is lip movement, whereas for ‘led’ there is not. This could be more accurately transcribed as . The movement is often protrusion or rounding, and the rounding can, in more extreme cases, involve puckering of the lips or contact between the upper teeth and lower lip. These more extreme cases could be transcribed as  is the IPA symbol for a labiodental approximant, i.e. a sound made between the lips and the teeth which is made with open approximation and no friction noise generated. (Some speakers actually do produce friction: this could be transcribed as . The symbol represents the fact that the two articulations are produced at the same time, rather than one after the other in sequence, as implied by .

Alveolar approximants often have another secondary articulation. Recall that for laterals, the main place of constriction is at the tongue tip, leaving the body and back of the tongue free to form other articulations. The same is equally true for [ɹ]. [ɹ] is frequently dark, or velarized. This is marked in trancription as . As with laterals, the degree of valorization is variable. Typically, speakers with clear initial laterals have darker initial rhotics; and speakers with darker initial laterals have clearer initial rhotics.

Commonly, [ɹ] is both labialized and velarized: . Just as [l] often loses its primary articulation at the tongue tip and instead the ‘secondary’ articulations are retained (so-called vocalization), so also [ɹ] sometimes loses its primary articulation at the tongue tip, but the secondary articulation of labialization is retained. Many speakers produce [r] as a labiodental approximant, ; or as a velarized labio - dental approximant, .

One way to understand non-rhotic accents is as varieties which have lost the tongue-tip articulation of [ɹ] syllable finally, leaving just vowel colouring. This is parallel with loss of tongue-tip articulation in the case of vocalized [l].