Abstrak Penelitian ini menganalisis perbedaan-perbedaan kecil dalam sebuah dialek/ bahasa dengan teori dialektologi. Tujuan penelitian ini adalah menjelaskan variasi-variasi fonologis, merekonstruksi fonologis, menjelaskan inovasi dan retensi yang terdapat pada isolek Pulaupandan, Pengasi dan Muak. Penelitian deskriptif ini bersifat sinkronis dan diakronis dengan pendekatan secara kualitatif-kuantitatif. Metode Pengumpulan data menggunakan metode cakap dan metode simak. Analisis data menggunakan metode padan fonetis artikulatoris dengan teknik pilah sebagai teknik dasar serta teknik hubung banding sebagai teknik lanjutan, sedangkan untuk menentukan status kebahasaan dan persentase kekerabatan digunakan metode dialektometri. Penyajian hasil analisis data digunakan metode formal dan metode informal. Berdasarkan hasil analisis sinkronis ditemukan variasi- variasi bunyi, yakni [a], [aɁ], [i], [u], [e], [ә], [o], [oɁ], [aw], [ew], [iy], [p], [b], [t], [k], [g], [m], [n], [ŋ], [ɲ], [s], [d], [h], [Ɂ], dan [l] dalam beberapa posisi. Berdasarkan hasil analisis diakronis ditemukan fonem PIBK dari hasil proses rekonstruksi protobahasa pada posisi tertentu. Fonem tersebut berupa enam fonem vokal dua gugus bunyi, yaitu vokal */i/, */u/, */e/,*/ә/, */o/ dengan luncuran gugus bunyi /oɁ/, dan */a/ dengan meluncurkan gugus bunyi/aɁ/ ; tujuh diftong */aw/, */ow/, */ew/, */iw/, */uw/ dan */iy/, */әy/ dan sembilan belasfonem konsonan */p/, */b/,*/t/, */k/, */g/, */m/, */n/, */ŋ/, */ɲ/, */s/, */d/, */h/, */Ɂ/,*/l/, */r/, */j/, */c/, */w/, dan */y/. Inovasi fonologis yang ditemukan berdasarkan kaidah perubahan bunyi, seperti: 1) metatesis; 2) afaresis; 3) pemecahan vokal; 4) apokop; dan 5) sinkop. Berdasarkan bukti-bukti sinkronis dan diakronis dengan menggunakan metode dialektometri serta hasil analisis data yang didapatkan di lapangan, IPp dinyatakan sebagai titik pengamatan yang masih mempertahankan isoleknya (konservatif). Kata Kunci: variasi, rekonstrusi, fonologi, dialektologi Abstract This research analyzed the small differences on dialect/language based on dialectology. The aims of this research are to explain the phonological variation, to reconstruct the phonological, and explain the phonological inovations and retentions found in Pulaupandan, Pengasi and Muak isolect. This descriptive study belongs to synchronic and diachronic with qualitative-quantitative approaches. The collecting of data used conversational method and participant observational method. Data analysis used phonetic articulatory method with sorting techniques as basic technique and comparating- connecting techniques as advanced techniques, while to determine the status of language and kinship percentage used dialectometry method. Presenting of data analysis results used formal and informal methods. Based on of the results analysis found variations synchronyc sounds, are, [a], [aɁ], [i], [u], [e], [ә], [o], [oɁ], [aw], [ew] , [iy], [p], [b], [t], [k], [g], [m], [n], [ŋ], [ɲ], [s], [d], [h], [Ɂ], and [l] in some positions. Based on the results of analysis diachronic found PIBK protolanguage phoneme from reconstruction process results in a certain position. That Phonemes form six vowels and two cluster sounds, they are; */i/, */u/, */e/, */ә/, */o/ with a glide group sound /oɁ/, and */a/ with launched cluster sound /aɁ/; seven diphthong */aw/, */ow/, */ew/, */iw/, */uw/ and */iy/, */әy/ and nineteen consonant phonemes */p/, */b/, */t/, */k/, */g/, */m/, */n/, */ŋ/, */ɲ/, */s/, */d/, */h/, */Ɂ/, */l/, */r/, */j/, */c/, */w/, and*/y/. Phonological inovations were found based on the rules of sound changes, such as: 1) metathesis;2) aphaeresis; 3) vowels breaking; 4) apocope; and 5) of syncope. Based on the evidences of synchronicand diachronic with used dialectometry method and the results of the analysis of data obtained in thefield, IPp expressed as an observation point which still retain its isolect (conservative). Keywords: variation, recontruction, phonology, dialectology