"Tin ear" is an idiom which originally meant was that someone was not able to appreciate music, was tone deaf, or was insensitive to differences in other kinds of sounds. It was then extended to also mean that someone was insensitive to subtle differences in a particular discipline or subtleties in what he/she was told. (Having a tin ear is different from turning a deaf ear in that the tin-eared seem to be unable to listen/understand if they wanted to.) Oddly enough, an 1867 West Point scrapbook gives "hunkey boy with a tin ear" as slang meaning "a lucky fellow" -- just about the opposite of every other use of the phrase.
The exact origin of the idiom is debatable. Merriam Webster gives 1935 as the date of first citation without giving a source. A.Word.A.Day simply stated that it was "from the idea of metal being incapable of sensation," but several readers wrote in to offer further ideas. One said that the use of tin particularly had a connotation of low value (as in tin-pot/tin pot dictator, tin pan alley, tin god, or Tin Lizzie) compared to other metals (it's certainly less complimentary than heart of gold or silver tongue) and said that the phrase had the additional meanings of "slang for a disfigured ear, an eavesdropper, and a slow telegrapher." Another reader offered the idea that ear trumpets for the hard of hearing had once been made of steel plated with tin to prevent rusting.
Tin Ear is also the name of two bands.
- One was a Philadelphia, Pennsylvania band influenced by 70's rock and described on allmusic.com as similar to Urge Overkill or Red Kross; this group released two albums, Gospel of TinEar in 1994 and Ballad of a Tin Band in 1996. The former was pretty much songwriter Dave Richards' project, with Luke Astro and Matt Coogan playing the drums at different times. Richards, Coogan, and bassist Ramone Sender toured for the first album and recorded the second, but then their label ShimmyDisc closed down. The band seems to still exist, since a Princeton, New Jersey radio station records an August 2002 visit by them.
- The other group to bear the name started out in the 1980s as composers/musicians Allan Loucks and David
Loucks and percussionist Robert Geddes. They did not start to record an album until 1993, and it was nearly finished when David Loucks was murdered during a robbery of his studio in March 1995. However, Allan decided to finish the self-titled "alternative/prog-rock" album which came out in 1996. Vocalist Brian Ledsford joined before their second CD, Name That Mood, "containing explorations into tone-poems, electronic, and film music." Spencer Hoveskeland was added as bassist and in the spring of 2000, they released their third CD, the "orchestral epic" Symphony in Three Movements.