Details: There are several sets of pieces that Bach collated (also) with his lessons in mind, amongst them the 'Orgelbuchlein', the 'Little Organ Book', which he started whilst working in Weimar in 1708, and the so-called 'Inventions and Sinfonias', composed in the 1720s in Cothen for his son Wilhelm Friedemann and for "lovers of the clavier, and particularly those who desire to learn". He worked on the 'Orgelbuchlein' over many years, adding to it and making changes, presumably adapting to his student's needs. His inscription on the title page proclaims in a rhyming couplet that his compositions were "in praise for the Almighty's will, and for my neighbour's greater skill". In the context of this programme two choral preludes and two 'Sinfonias' are used as "warm-ups", or preludes for five imagined lessons, functioning as the binding of the student's portfolio.