In the plural it is often the melody that changes, not the consonants.
In Bamum the plural is not primarily a matter of segments: it is a matter of melody.
In the singular the class prefix carries either a high or a low tone. In the plural it most often carries an HL pattern, and triggers a downstep on what follows.
singular — a small tree
plural — small trees
The arrow ↓ is not a letter: it shows that the following high tone is realised one step lower. This is called downstep, very widespread in the Grassfields languages.
🧠 Practical consequence: if you pronounce the right syllables but the wrong melody, you may say "a tree" while believing you said "trees".