The present study aims to investigate the opposing tendencies of innovation and conservatism in the phonetic and phonological domains in Arabic. It draws a parallel between sound changes that occurred in the standard variety and the retention of specific phonetic and phonological aspects in the dialectal varieties. Recent works have highlighted three bases of sound change: phonetic, structural and social causes. The phonetic basis of sound change has been challenged from an articulatory, acoustic, aerodynamic and perceptual point of view, but also from a coarticulatory one as is illustrated here by the evolution of the phonetic properties of classical Arabic’s four consonants (〈sīn〉 (س) /s/, 〈šīn〉 (ش) /ʃ/, 〈ḍād〉 (ض) /dʕ/ and 〈ğīm〉 (ج) /ʒ/). Other coarticulatory bases are proposed to explain the retention of some old phonetic and phonological traits in modern Arabic dialects, such as the preservation of the long mid vowels ē /eː/ and ō /oː/, the evolution of the interdental fricative consonants 〈z̩ā’〉 /ðʕ/, 〈thā’〉 /θ/ and 〈dhal〉 /ð/ and the uvular stop 〈qāf〉 /q/ and the tendency to depharyngealise the consonants 〈ṭā’〉 (ط) /tʕ/, 〈ḍād〉 (ض) /dʕ/, 〈s̩ād〉 (ص) /sʕ/ and 〈z̩ā’〉 (ظ) /ðʕ/.