Source:[2][3] There are two series of stops and affricates in Hakka, both voiceless: tenuis /p t ts k/ and aspirated /pʰ tʰ tsʰ kʰ/.
Before that happened, the four Middle Chinese 'tones', ping, shang, qu, ru, underwent a voicing split in the case of ping and ru, giving the dialect six tones in traditional accounts.
These so-called yin-yang tonal splittings developed mainly as a consequence of the type of initial a Chinese syllable had during the Middle Chinese stage in the development of Chinese, with voiceless initial syllables [p- t- k-] tending to become of the yin type, and the voiced initial syllables [b- d- ɡ-] developing into the yang type.
Hakka preserves all of the entering tones of Middle Chinese and it is split into two registers.
Meixian has the following: Middle Chinese entering tone syllables ending in [k] whose vowel clusters have become front high vowels like [i] and [e] shifts to syllables with [t] finals in modern Hakka[7] as seen in the following table.