Bits and Pieces: The Penguin Book of Rock and Pop Facts and Trivia (Steve Smith 1988) has a useful section on silence in music. Naturally it starts with John Cage's piece entitled 4′33". I have seen the sheet music for this which, as I recall, has instructions about opening a piano and closing it at the end, after 4 minutes 33 seconds of obligatory silence. Smith notes that the performer, 'usually a pianist,' is expected to use his fingers to show the audience which of the song's three parts they are listening to… In Wikipedia's piece they mention that Frank Zappa recorded it as part of A Chance Operation: The John Cage Tribute on the Koch label in 1993. It was also recorded by Swedish electronic rockers Covenant in 2000 (the piece was entitled You Can Make Your Own Music.)
4'33" was first publicly performed in 1952. In 1953 CBS issued a blank record entitled 3 Minutes of Silence - it was intended for juke boxes, enabling those tired of the music to purchase a few minutes of peace and quiet. Steve Smith notes 'Hush records released a similar disc in 1959.'
The last note of She's Leaving Home on The Beatle's Sergeant Pepper album lasts 43 seconds - the last part of which appears to be silence but is at a high frequency only audible to dogs.
Allison Crowe on her 2010 album Spiral has a track Silence (82 seconds of) which can be 'heard' here.
John Lennon played around with silence several times. There is his three second silent Nutopian National Anthem from his 1973 Mind Games album and Two Minutes Silence on his 1969 Unfinished Music No.2: Life With The Lions. This silent tribute was for John Ono Lennon II, the child that John and Yoko lost to a miscarriage in 1968. Silent tributes probably form a whole subsection…
On the 2005 album World Play by Soul SirkUS tracks 16 and 17 both called Soulspace are silent.
Smith notes that the title track of Afrika Bambaataa's 1986 LP Beware (The Funk is Everywhere) 'is a band of silence.'
Magic Records (actually Stiff records 'in disguise') released an album in the 1980 called The Wit and Wisdom of Ronald Reagan. It consisted of two 20 minute blank/ silent sides.Apparently John Denver has a similar silent track The Ballad of Richard Nixon. Another blank track is The Ten Coolest Things about New Jersey by The Bloodhound Gang. Similar blank gag books abound…The Wisdom of Sarah Palin, The Banker's Book of Ethics etc.,
Smith also records attempts to sell the silent space between tracks on LPs for advertising - notably by Sigue Sigue Sputnik and (with irony) by The Who (on The Who Sell Out.) At Wikipedia's invaluable Silent Musical Compositions there are about 100 instances including tracks by rock avant-gardists such as Robert Wyatt, Crass,Coil, Brian Eno and The Melvins. Before John Cage's composition they list three silent works - including Monotone-Silence Symphony (1949), by the distinguished French artist Yves Klein - the composition was 'in two movements, a single 20-minute sustained chord followed by a 20-minute silence...'