The "Appassionata" was his 23rd piano sonata
The "B" in "BCE"
The "B" in "FBI"
The "B" in G.B.S.
The "B" in GB
The "B" in its name stands for "brush"
The "B" in KB and MB
The "B" in L.B.J.
The "B" in Roy G. Biv
The "B" in TV's former The WB network
The "B" of 11-Across
The "B" of B.S.A.
The "b" of BCE
The "B" of F.B.I.
The "B" of MB
The "B" of N.B.
The "B" of Roy G. Biv
The "Ba" of BaSO4
The "BA" of the Boston museum MOBA
The "Barry Trotter" books, et al.
The "Bel Paese," to locals
The "Big Board," on Wall St.
The "Black Paintings" and others
The "black" in black ice
The "blood" in bloodstone
The "Blue Monster," to golfers
The "Butcher of Uganda"
The "c" in a + b = c
The "C" in C-SPAN
The "C" in C.S. Lewis
The "C" in CMYK
The "c" in etc.
The "C" in N.Y.C.
The "C" in T.L.C.
The "C" in the musical instruction "D.C. al fine"
The "C" in U.P.C.
The "C" in UPC
The "C" in USMC
The "C" of C. S. Lewis
The "C" of CNN
The "C" of D.R.C.
The "C" of F.C. Barcelona
The "C" of FDIC: Abbr.
The "C" of I.C.U.
The "C" of SPCA
The "C" of TLC
The "C" of U.S.M.C.
The "cave" of "cave canem"
The "cetera" of "et cetera"
The "Claudius" in Tiberius Claudius Nero
The "common" sort is said to be not so common
The "D" in CD
The "D" in DJ
The "D" in DOT
The "D" in F.D.A.
The "D" in F.D.R.
The "D" in J.D. Salinger
The "D" in jazz's Miss D
The "D" in R&D: Abbr.
The "D" in UCSD
The "D" of "NORAD"
The "D" of C.D.
The "D" of D.E.A.
The "D" of D.J.
The "D" of FDA
The "D" of John D. Rockefeller
The "D" of LED
The "D" of PRNDL
The "da-da-da-DUM!" of Beethoven's Fifth
The "daily grind"
The "Dalai" of "Dalai Lama" is Mongolian for this
The "Dark Star" trilogy, for example
The "day" in "seize the day"
The "Demon Star"
The "dial" in "Don't touch that dial"
The "Divine" Bette
The "doll" in Ibsen's "A Doll's House"
The "E. B" of E. B. White
The "E." in A.E.S.
The "e" in "est"
The "e" in "eu"
The "E" in 34-Down
The "E" in 64-Across
The "E" in 68-Across
The "E" in B.C.E.
The "E" in B.P.O.E.
The "E" in BCE
The "E" in DOE: Abbr.
The "E" in E = mc2
The "E" in E. & J. Gallo
The "E" in E. L. Doctorow
The "E" in E.R.: Abbr.
The "E" in E.S.L.: Abbr.
The "E" in EGBDF
The "E" in Einstein's special relativity equation
The "E" in EMT: Abbr.
The "E" in ERA
The "E" in ESL: Abbr.
The "E" in FEMA: Abbr.
The "e" in Genoa?
The "E" in H.R.E.: Abbr.
The "E" in HOMES
The "e" in i.e.
The "E" in IBPOEW
The "E" in literary monogram TSE
The "E" in literary monograms
The "E" in N.L.E.
The "E" in NATO's alphabet
The "E" in P.G.&E.: Abbr.
The "E" in PG&E: Abbr.
The "E" in Q.E.D.
The "E" in the HOMES mnemonic
The "E" of "E-mail"
The "E" of 12-Down
The "E" of 14-Across
The "E" of 30-Down
The "E" of accounting's EY
The "E" of AEC
The "E" of B.P.O.E.
The "E" of BPOE
The "E" of E.S.L.: Abbr.
The "E" of E.U.: Abbr.
The "E" of EGBDF
The "E" of G.E.: Abbr.
The "E" of H.R.E.
The "E" of N.E.A.: Abbr.
The "E" of N.Y.E.
The "E" of PETA
The "E" of Q.E.D.
The "E" of R.E.O. Speedwagon
The "E" of Ransom E. Olds
The "E" of REO
The "E" of the old NY&E Rail Road
The "E" of the REO Speed Wagon
The "E" on a baseball scoreboard
The "e" sound in "tandem"
The "e" sound in "the," e.g.
The "e" sound in "they," e.g.
The "Ed" of Con Ed
The "emptor" in "caveat emptor"
The "et" of et cetera
The "eye" in network TV
The "F" and "B" of Samuel F. B. Morse, e.g.: Abbr.
The "F" in AFI
The "F" in F = ma
The "f" in f-number
The "f" in f-stop
The "F" in F.Y.I.
The "F" in KFC
The "F" in SPF
The "F" in TGIF: Abbr.
The "F" in the equation "F = ma"
The "F" in UHF: Abbr.
The "F" in USAF
The "F" of FBI
The "f" of fwiw
The "F" of PDF
The "F" of R.A.F.
The "F" of T/F
The "fact" that bulls get angry when they see the color red, e.g.
The "fact" that the Great Wall of China is visible from space, and others
The "fat lady" in a phrase
The "few" in a Churchill speech
The "fight or flight" emotion
The "first" in "first and ten"
The "five" in "take five," e.g.
The "fizz" in a gin fizz
The "for" side
The "forbidden dance" of the early '90s
The "Free Willy" creature
The "G" in 30-Down
The "g" in e.g.
The "G" in EGBDF
The "G" in EKG
The "G" in G&T
The "G" in GTO
The "G" in SAG
The "G" of "TGIF"
The "G" of GTO
The "G" of L.G.B.T.
The "G" of L.G.B.T.Q.+
The "G" of LGBTQIA+
The "Gee" in Bee Gees
The "genu" in "genuflect"
The "gods" in "Chariots of the Gods?," in brief
The "gone girl" in "Gone Girl"
The "good stuff" on the table
The "Good Times" family
The "good" chocolate
The "good" silver is often stored in it
The "greatest blessing" and the "greatest plague": Euripides
The "H. G." of H. G. Wells
The "H" in "M*A*S*H": Abbr.
The "H" in Hanukkah
The "H" in Hellenic
The "H" of HR
The "Habanera" from "Carmen," e.g.
The "Hallelujah" Chorus is part of it
The "Harry Potter" books, e.g.
The "heel" of the Arabian Peninsula
The "height" part of a fear of heights
The "height" part of a height phobia
The "her" in Beethoven's question "Who comprehends her?"
The "her" in Broadway's "I've Grown Accustomed to Her Face"
The "her" in Shakespeare's "Age cannot wither her, nor custom stale / Her infinite variety"
The "her" in the lyric "I met her in a club down in old Soho"
The "her" of "I've Grown Accustomed to Her Face"
The "her" of "leave her to heaven"
The "high heel" of Italy's "boot"
The "him" in the 1939 film line "I won't let you take him!"
The "Home Alone" boy, e.g.
The "home" in John Denver's "Take Me Home, Country Roads"
The "Homo" in "Homo sapiens"
The "Homo" of "Homo sapiens"
The "I" in "The King and I"
The "I" in 23-Down
The "I" in E. I. du Pont
The "I" in F.W.I.W.
The "I" in I. M. Pei
The "I" in I.B.M.: Abbr.
The "I" in ICBM
The "I" in IHOP: Abbr.
The "I" in IUD
The "I" in IV
The "I" in M.I.T.: Abbr.
The "I" in MIT (abbr.)
The "I" in ROYGBIV
The "I" in T.G.I.F.
The "I" in TGIF
The "I" in the answer to 1-Across
The "I" in VMI: Abbr.
The "I" of "How I Met Your Mother"
The "I" of "The King and I"
The "I" of Canada's P.E.I.
The "I" of Claudius I
The "I" of E. I. du Pont
The "I" of Elizabeth I?
The "I" of F.Y.I., for short
The "I" of FBI, e.g.
The "I" of FWIW
The "I" of I. M. Pei
The "I" of I.M.F.: Abbr.
The "I" of I.P.A.
The "I" of ICBM
The "I" of IM
The "I" of IM, sportswise
The "I" of IV
The "I" of literature's "Reader, I married him"
The "I" of R.P.I.: Abbr.
The "I" of T.G.I.F.