A high-quality modern recording of a core piece of the piano repertoire? Completely free? Legally?
"Johann Sebastian Bach (1685-1750) was a German composer, organist, harpsichordist, violist, and violinist whose sacred and secular works for choir, orchestra, and solo instruments drew together the strands of the Baroque period and brought it to its ultimate maturity. Although he did not introduce new forms, he enriched the prevailing German style with a robust contrapuntal technique, an unrivalled control of harmonic and motivic organisation, and the adaptation of rhythms, forms and textures from abroad, particularly from Italy and France.
Revered for their intellectual depth, technical command and artistic beauty, Bach's works include the Brandenburg Concertos, the Goldberg Variations, the Partitas, The Well-Tempered Clavier, the Mass in B minor, the St Matthew Passion, the St John Passion, the Magnificat, the Musical Offering, The Art of Fugue, the English and French Suites, the Sonatas and Partitas for solo violin, the Cello Suites, more than 200 surviving cantatas, and a similar number of organ works, including the famous Toccata and Fugue in D minor and Passacaglia and Fugue in C minor, and the Great Eighteen Chorale Preludes and Organ Mass.
Bach's abilities as an organist were highly respected throughout Europe during his lifetime, although he was not widely recognised as a great composer until a revival of interest and performances of his music in the first half of the 19th century. He is now generally regarded as one of the main composers of the Baroque style, and as one of the greatest composers of all time."
This is a selection of videos showing good performances of some of the pieces on the Trinity Guildhall grade 8 violin syllabus.
Granados: "Danse Espagnole", arranged by Kreisler:
I found myself yesterday trying to explain the evolution of equal temperament, off the top of my head, which I never do a particularly good job of...not least because it's not really anything I could call a speciality. Something I find particularly difficult is making the jump from abstract mathematical concepts to how the sounds of earlier tuning systems exploited the character of individual keys which resulted.