# - Relationship to original unknown
0 - Original key
1 - Transposed key
# - Undefined
|$a - Key (NR)
$6 - Linkage (NR)
|$8 - Field link and sequence number (R)
The set of pitch relationships that establishes a single pitch class as a tonal centre for a musical work or expression. May be used to differentiate a musical work or expression from another with the same title.