documentclass[margin=10pt]{standalone}

title{Analogue Synthesizer block diagram}

usepackage{tikz}
begin{document}

%Define standard Block diagram node styles
tikzstyle{block} = [draw, rectangle, minimum height=3em, minimum width=6em]
tikzstyle{line} = [draw, -stealth, thick]

begin{tikzpicture}[scale=2]

  % Blocks
  draw (2,1) node[block] (LFO) {LFO};
  draw (2,0) node[block] (VCO1) {VCO1};
  draw (4,0) node[block] (VCF) {VCF};
  draw (4,-1) node[block] (ADSR1) {ADSR};
  draw (6,0) node[block] (VCA) {VCA};
  draw (6,-1) node[block] (ADSR2) {ADSR};
  draw (0,-2) node[block] (Midi to CV) {MIDI to CV};
  draw (0,-3) node[block] (Keyboard) {MIDI Keyboard};

  % Lines
  path[line] (LFO) -- (VCO1);
  path[line] (VCO1) -- (VCF);
  path[line] (VCF) -- (VCA);
  path[line] (ADSR1) -- (VCF);
  path[line] (ADSR2) -- (VCA);
  path[line] (Keyboard) -- (Midi to CV);
  path[line] (Midi to CV.north) |- node[yshift=-4em, xshift=0.5em,fill=white]{1V/Octave} (VCO1);
  path[line] (Midi to CV.east) -| node[yshift=0em, xshift=0em]{} (ADSR2.south);
  path[line] (Midi to CV.east) -| node[yshift=0em, xshift=-4em,fill=white]{Gate} (ADSR1.south);

end{tikzpicture}
end{document}