The Symphonies (or Sinfonias) Wq 182/6 by Carl Philipp Emanuel Bach (sometimes referred to as the 'Hamburg Bach', since that was where he spent the latter part of his career) were commissioned by Baron Gottfried van Swieten in 1773. These are very modern compositions, brimming with audacity and vitality, elegant music but which nevertheless makes great technical demands and requires a good deal of thorough groundwork.