These are the names of the fields used by ABC, along with their equivalents in this website.

X - X_number
T - Title
A - Area
B - Bibliography
C - Composer
D - Discography
E - abc_E
F - File
G - Groups
H - History
I - abc_I
J - abc_J
L - Length
M - Time_Signature
N - Notes
O - Country
P - Part_Order
Q - Tempo
R - Rhythm
S - Source
U - Macros
V - Voice
W - Words
Y - abc_Y
Z - Transcriber
w - words
K - Key_Signature