bach / batch are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
bach: (noun) German baroque organist and contrapuntist; composed mostly keyboard music; one of the greatest creators of western music (1685-1750). (noun) the music of Bach.
batch: (noun) all the loaves of bread baked at the same time. (noun) (often followed by `of') a large number or amount or extent. (noun) a collection of things or persons to be handled together. (verb) batch together; assemble or process as a batch.
bach: b·AA·k
batch: b·AE·ch
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)