From the Sinclair Wiki :
SpecBAS is an improved implementation of Sinclair BASIC for x86 PCs running Windows or Linux operating systems. SpecBAS is a 32bit application.
SpecBAS is an interpreter for a dialect of BASIC, based on Dartmouth BASIC, as was the original Sinclair BASIC. SpecBAS adds many new commands and functions such as procedures, math functions and sound using samples and music .mod files. Although not as fast as compiled languages, it is very quick.
Github Project Page and Source Code Demos
Paul Dunn's The SpecBAS Reference Manual (and SpecOS_reference.doc)
Paul Dunn's YouTube Videos