I have a longtable in which the last column is too wide. How do I fix this table?
\documentclass[12pt, a4paper, onecolumn, oneside, final]{report}
\makeatother
\usepackage{array}
\setlength\extrarowheight{4pt}
\usepackage{tabto}
\newenvironment{tabs}[1]
{\TabPositions{#1}}
\usepackage{longtable}
\newcolumntype{R}[1]{>{\raggedleft\arraybackslash}p{#1}}
\newcolumntype{L}[1]{>{\raggedright\arraybackslash}p{#1}}
\usepackage{multicol}
\usepackage{multirow}
\usepackage{musicography}
\begin{document}
\begingroup
\setlength{\LTleft}{-20cm plus -1fill}
\setlength{\LTright}{\LTleft}
\begin{small}
\begin{longtable}{|p{1cm}|p{2cm}|p{2cm}|}
\caption{\textit{Pitch class} yang digunakan dalam penelitian}
\label{tbl:pitchClassUsed}\\
\hline
{\textbf{No}} & {\textbf{No. MIDI}} & {\textbf{\textit{Pitch Class}}} \bigstrut\\
\endfirsthead
\multicolumn{3}{c}{\textbf{\tablename~\thetable} \textit{Pitch class} yang digunakan dalam penelitian (Lanjutan)}\\
\hline
{\textbf{No}} & {\textbf{No. MIDI}} & {\textbf{\textit{Pitch Class}}} \bigstrut\\
\endhead
\hline
1 & 0 & \multicolumn{1}{l|}{0} \bigstrut\\
\hline
2 & 30 & F$\musSharp$1 / G$\flat$1 \bigstrut\\
\hline
3 & 31 & G1 \bigstrut\\
\hline
4 & 32 & G$\musSharp$1 / A$\flat$1 \bigstrut\\
\hline
5 & 33 & A1 \bigstrut\\
\hline
6 & 34 & A$\musSharp$1 / B$\flat$1 \bigstrut\\
\hline
7 & 35 & B1 \bigstrut\\
\hline
8 & 36 & C2 \bigstrut\\
\hline
9 & 37 & C$\musSharp$2 / D$\flat$2 \bigstrut\\
\hline
10 & 38 & D2 \bigstrut\\
\hline
11 & 39 & D$\musSharp$2 / E$\flat$2 \bigstrut\\
\hline
12 & 40 & E2 \bigstrut\\
\hline
13 & 41 & F2 \bigstrut\\
\hline
14 & 42 & F$\musSharp$2 / G$\flat$2 \bigstrut\\
\hline
15 & 43 & G2 \bigstrut\\
\hline
16 & 44 & G$\musSharp$2 / A$\flat$2 \bigstrut\\
\hline
17 & 45 & A2 \bigstrut\\
\hline
18 & 46 & A$\musSharp$2 / B$\flat$2 \bigstrut\\
\hline
19 & 47 & B2 \bigstrut\\
\hline
20 & 48 & C3 \bigstrut\\
\hline
21 & 49 & C$\musSharp$3 / D$\flat$3 \bigstrut\\
\hline
22 & 50 & D3 \bigstrut\\
\hline
23 & 51 & D$\musSharp$3 / E$\flat$3 \bigstrut\\
\hline
24 & 52 & E3 \bigstrut\\
\hline
25 & 53 & F3 \bigstrut\\
\hline
26 & 54 & F$\musSharp$3 / G$\flat$3 \bigstrut\\
\hline
27 & 55 & G3 \bigstrut\\
\hline
28 & 56 & G$\musSharp$3 / A$\flat$3 \bigstrut\\
\hline
29 & 57 & A3 \bigstrut\\
\hline
30 & 58 & A$\musSharp$3 / B$\flat$3 \bigstrut\\
\hline
31 & 59 & B3 \bigstrut\\
\hline
32 & 60 & C4 \bigstrut\\
\hline
33 & 61 & C$\musSharp$4 / D$\flat$4 \bigstrut\\
\hline
34 & 62 & D4 \bigstrut\\
\hline
35 & 63 & D$\musSharp$4 / E$\flat$4 \bigstrut\\
\hline
36 & 64 & E4 \bigstrut\\
\hline
37 & 65 & F4 \bigstrut\\
\hline
38 & 66 & F$\musSharp$4 / G$\flat$4 \bigstrut\\
\hline
39 & 67 & G4 \bigstrut\\
\hline
40 & 68 & G$\musSharp$4 / A$\flat$4 \bigstrut\\
\hline
41 & 69 & A4 \bigstrut\\
\hline
42 & 70 & A$\musSharp$4 / B$\flat$4 \bigstrut\\
\hline
43 & 71 & B4 \bigstrut\\
\hline
44 & 72 & C5 \bigstrut\\
\hline
45 & 73 & C$\musSharp$5 / D$\flat$5 \bigstrut\\
\hline
46 & 74 & D5 \bigstrut\\
\hline
47 & 76 & E5 \bigstrut\\
\hline
48 & 77 & F5 \bigstrut\\
\hline
49 & 81 & A5 \bigstrut\\
\hline
50 & 83 & B5 \bigstrut\\
\hline
51 & 85 & C$\musSharp$6 / D$\flat$6 \bigstrut\\
\hline
\end{longtable}%
\end{small}%
\end{document}
\multicolumn{3}{c}
. Once I removed this, the column had the expected size.\setlength{\LTleft}{-20cm plus -1fill}
which means that if the natural width of the table is 1cm narrower than the page, instead of supplying 1cm white soace to fill the gap it removes 1cm so making teh table 2cm too narrow. What is the intention of the -1fill ?