The published volumes include symphonies that can be attributed to Leopold Mozart with great certainty, as well as those whose authenticity is rather uncertain and even some likely not composed by him but passed down under his name. The compositions were created between the early 1750s and the mid-1760s, with one possibly dating as late as 1771. This spans a compositional spectrum from basso continuo music to a “modern” style influenced by leading Italian music. Most of the symphonies have three movements. The standard instrumentation of four strings and two horns—dispensing with violas in the symphonies with a motto—is often reduced to strings alone, but occasionally expanded to include trumpets and timpani or oboes.