He wrote 10

What now it's called Bach's sonatas for cello and piano, are the 3 sonatas for viola da gamba and harpsichord BWV 1027-1029. The second sonata, BWV 1028 is in the tonality of D major.

Darrell Matthews Berg has written:

'The keyboard sonatas of C.P.E. Bach' -- subject(s): History and criticism, Music, Musical Style, Sonatas (Piano), Sonatas(Piano), Style, Musical

Carl Philipp Emanuel Bach has written:

'Music Minus One Cello'

'Sonata' -- subject(s): Sonatas (Violin and harpsichord), Sonatas (Flute and harpsichord), Sonatas (Harpsichord), Trio sonatas (Violins (2), continuo), Sonatas (Violoncello and piano), Arranged

'Solfegietto in C minor' -- subject(s): Accessible book

'The Prussian sonatas' -- subject(s): Sonatas (Harpsichord), Sonatas (Piano)

'Verzeichniss des musikalischen Nachlasses des verstorbenen Capellmeisters Carl Philipp Emanuel Bach ..' -- subject(s): Music, Bibliography

'Sonatas, fantasies and rondos for piano solo' -- subject(s): Harpsichord music

'Heilig ist Gott' -- subject(s): Choruses, Sacred (Mixed voices) with orchestra, Vocal scores with organ

'Bach Organ Music'

'6 pieces, for clarinet, bassoon and piano' -- subject(s): Trios (Harpsichord, bassoon, clarinet), Trios (Harpsichord, 2 clarinets), Arranged, Trios (Harpsichrod, clarinet, saxophone), Arranged

'Essay on the true art of playing keyboard instruments'

'Concerto in A Major, H 437-39, Wq 168, 172, 69'

'Briefe und Dokumente' -- subject(s): Correspondence, Composers

'James Galway plays Stamitz' -- subject(s): Concertos (Flute), Sonatas (Flute)

'Concerto for piano in D minor' -- subject(s): Concertos (Harpsichord with string orchestra), 2-piano scores, Scores

'Great Keyboard Sonatas Series II'

'Piano Solo'

'Six sonatas for organ' -- subject(s): Sonatas (Organ), Sonatas (Organ), Arranged

'Sonatas, fantasies and rondos for clavier'

'Four Sonatas'

'Auferstehung und Himmelfahrt Jesu' -- subject(s): Oratorios, Scores

'Bach Music Master'

He wrote 18 sonatas for piano. There is also a traditional "19th" sonata which consist of two separate works usually performed as a complete sonata. He wrote 17 church sonatas. He wrote 36 violin sonatas. He also wrote 3 other chamber sonatas, one for bassoon and cello, and two for violin and bass.

If my math is correct, he wrote 75 sonatas.