Can anybody tell me what this chord with an ø symbol after F# is? The key signature is E minor.
A quick Google search which amounted to "what does a circle with a cross through it mean?" turns up this: http://ultimate-guitar.com/forum/archive/index.php?t-637414.html
The answer is: "Ø = half diminished, aka m7b5"
This particular chord is played on piano as
Credit to PianoChord.com
It is indeed half-diminished. A diminished chord has root, m3, b5 and bb7. In F#o it'll be F#, A, C and Eb. The half dim., a.k.a. m7b5 differs only by the m7; E instead of Eb. Its 1st inversion is the root (inversion/position) of Am6.
The symbol you refer to is a minor 7 flat 5 chord, also called half diminished. While reading music, or writing it, it is easier to read the symbol than the longer version which would be F#-7b5. This symbol also represents the sixth scale degree of the melodic minor scale.