Production of learned vocalizations requires precise selection and accurate sequencing of appropriate vocal-motor actions. The basal ganglia are essential for the selection and sequencing of motor actions, but the cellular specializations and circuit mechanisms governing accurate sequencing of vocalizations are unknown. Here, we use single-nucleus RNA sequencing and genetic manipulations to map basal ganglia cell types and circuits involved in the production of songbird vocal sequences. We identify cell-type specializations in direct-like and indirect-like basal ganglia pathways, including evolutionary expansion of striatal and arkypallidal cell-types that could facilitate vocal sequencing. We also reversibly reduced the expression of FoxP2 with a viral knockdown. For birds in which FoxP2 was knocked down, striatal neurons exhibited decreased expression of Drd1 and showed an increased ratio of Drd2/Drd1 expression. These findings identify key evolutionary specializations and circuits essential for selection and sequencing of vocal-motor actions necessary for vocal communication. Overall design: We carried out single-nuclei RNA-sequencing of zebra finch Area X. Each bird received an AAV injection of a hairpin directed to knockdown FoxP2 or a scrambled control hairpin. Two birds for each condition were pooled.