The Natures
Natural SingLets keep the familiar letter names A, B, C, D, E, and G, while F shifts to Fi. In pronunciation, these correspond to /eɪ/, /bi/, /si/, /di/, /i/, /fi/, and /dʒi/.
Note F gets rid of its alphabetic pronunciation of /ɛf/, two discrete phones, and obtains /fi/, a CV.
This lets the natural domain preserve direct letter-name identity while improving singability where it is most needed.
The Onset Logic
Going to the accidentals, E variants are given a consonant onset "/j/" as "y" as in "yeh /jɛ/" to have CV SingLets.
The consonant onsets are: A→/-/ (missing), B→/b/, C→/s/, D→/d/, E→/j/, F→/f/, and G→/dʒ/.
These are the foundations for A-G pitch classes, permitting a systematic design for using distinctively V (and VN) rhymes to flag both accidental directions (sharp vs flat) and accidental tiers (single, double, ...).
The Rhyme Progression
Accidental directions (sharp vs flat) and tiers (single, double, etc.) are distinguished by systematic vowel shifts. Natural notes rhyme with a bright vowel /i/, single and double sharp SingLets move toward darker vowels (/ɑ/ and /ɔ/), and flat SingLets toward /ɛ/ and /u/, respectively. These create a mnemonic ladder from bright to dark vowels.
Higher tiers extend the system to /ɑn/ and /ɔŋ/ for triple and quadruple sharp notes, and /ɛn/ and /uŋ/ for triple and quadruple flat notes.