English Phonetics/ConsonantR

As was mentioned, the English phonetic system contains the allophones of some consonants (the plosives and the L). If we add the voiced counterparts of these consonants, this gives us around 3 possible for replace the consonant.

Plosives
As said before, the user can replace the plosives for aspirated allophones without major issues due to sounding practically identical, just varying in the stress and air release. If a consonant sounds too strident or too weak, it's possible to replace it with the corresponding allophone.

In the case of the voiced counterparts, these ones usually can be used as allophones at the end of the syllable, where the voicing contrast is minor and the consonant are prone to voicing assimilation phenomena. This isn't limited exclusively to the plosives, but to the sibilants as well, specially the voiceless [s] and its voiced counterpart [z].

Liquid consonant
The L has two allophones: the Clear L, used at the beginning of and

The Dark L is prone to be replaced to a vowel in a process called L-vocalization. Due to its (labio)velar quality, this one shifts to a close back vowel as u:, U or o. Knowing this is possible replace the phoneme [l] for a close back vowel as [u:] or [U] if the user seeks to imitate this process.

Alternatively the user can add a short close back vowel for improve the sound of the consonant and even stretch it as generally the consonant stands better to between two vowels (remember that usually the Dark L doesn't stand to be alone in a note, with exception of Luka's). This last tip can be aided further more with the use of the Vocaloid3's devoiced vowels.