Align levels in a tree using tikz-qtree

Question

I'd like all levels in my tree diagram to be aligned vertically. The problem is that some branches 'skip' a level. Specifically, all x's and all C's should be next to each other (the rest is fine as it is). I managed to to this for the x's by specifying the distance from the root. But the C's are all over the place.

\documentclass[12pt]{beamer}
\usepackage{tikz}
\usepackage{tikz-qtree}

\begin{document}
\begin{frame} 
\begin{tikzpicture}
\tikzset{frontier/.style={distance from root=150pt}}
    \Tree   [.{\textbf{W}} 
                [.{\textbf{S}} 
                    [.\textit{Onset} [.C {\textit{xx}} ] 
                                    [.C {\textit{x}} ] ] 
                    [.\textit{Reim}
                        [.\textit{Nukleus}  [.C {\textit{x}} ]
                                    [.C {\textit{x}} ] ]
                        [.\textit{Koda}         {C} ] ] ]
                [.{\textbf{S}} 
                    [.\textit{Onset} [.C {\textit{x}} ] ]
                    [.\textit{Reim }    
                        [.\textit{Nukleus} [.C {\textit{x}} ] ]
                        [.\textit{Koda} {C} {C} ] ] ]
                            ]
\end{tikzpicture}
\end{frame}
\end{document}

with your code i obtain the following image:

Answer 1

I agree with cfr that forest is the way to go for this kind of tree, but if you have a lot of them and you don't mind some branches looking a bit odd you could simply add extra brackets around the nodes that are at the wrong level.

\documentclass[12pt]{beamer}
\usepackage{tikz}
\usepackage{tikz-qtree}
\tikzset{every tree node/.style={font=\itshape}}

\begin{document}
\begin{frame} 
\begin{tikzpicture}
\tikzset{frontier/.style={distance from root=150pt}}
    \Tree   [.{\textbf{\upshape W}} 
                [.{\textbf{\upshape S}} 
                    [.Onset  [[.C {xx} ]] 
                [[.C {x} ]] ] 
                    [.Reim
                        [.Nukleus  [.C {x} ]
                                    [.C {x} ] ]
                        [.Koda       [.C  {x} ] ] ] ]
                [.{\textbf{\upshape S}} 
                    [.Onset [[.C {x} ]] ]
                    [.Reim     
                        [.Nukleus [.C {x} ] ]
                        [.Koda [.C {x} ] [.C {x} ] ] ] ]
                            ]
\end{tikzpicture}
\end{frame}
\end{document}

The extra x nodes I added to the tree don't affect the placement of the Cs. You can still align the C nodes and the x nodes even with missing x nodes:

\documentclass[12pt]{beamer}
\usepackage{tikz}
\usepackage{tikz-qtree}
\tikzset{every tree node/.style={font=\itshape}}

\begin{document}
\begin{frame} 
\begin{tikzpicture}
\tikzset{frontier/.style={distance from root=150pt}}
    \Tree   [.{\textbf{\upshape W}} 
                [.{\textbf{\upshape S}} 
                    [.Onset  [[.C {xx} ]] 
                [[.C {x} ]] ] 
                    [.Reim
                        [.Nukleus  [.C {x} ]
                                    [.C {x} ] ]
                        [.Koda       [.C   ] ] ] ]
                [.{\textbf{\upshape S}} 
                    [.Onset [[.C {x} ]] ]
                    [.Reim     
                        [.Nukleus [.C {x} ] ]
                        [.Koda [.C  ] [.C  ] ] ] ]
                            ]
\end{tikzpicture}
\end{frame}
\end{document}

Answer 2

Since nobody has yet answered, here's a Forest version:

\documentclass[border=10pt]{standalone}
\usepackage[linguistics]{forest}
\begin{document}
\begin{forest}
  before typesetting nodes={
    where level<=1{font=\bfseries}{if content={C}{tier=c}{font=\itshape, if content={x}{tier=x}{}},}
  },
  [W 
    [S
      [Onset
        [C[xx]][C[x]]
      ]
      [Reim
        [Nukleus
          [C[x]] [C[x]]
        ]
        [Koda
          [C]
        ]
      ]
    ]
    [S
      [Onset
        [C[x]]
      ]
      [Reim
        [Nukleus
          [C[x]]
        ]
        [Koda
          [C][C]
        ]
      ]
    ]
  ]
\end{forest}
\end{document}

The nice thing about this, of course, is that Forest does all the work: no need to hard-code distances or change them if the content or structure of the tree is modified later.

Answer 3

After some trial and error I've just settled on specifying nodes and then moving each node individually. This is a bit tedious and I'll have to do it for every individual tree, so if someone has a better solution, please tell me.

Here's the code:

\documentclass[12pt]{beamer}
\usepackage{tikz}
\usepackage{tikz-qtree}

\begin{document}
\begin{frame} 
    \begin{tikzpicture}
    \tikzset{frontier/.style={distance from root=150pt}}
    \Tree   [.{\textbf{W}} 
    [.{\textbf{S}} 
    [.\textit{Onset} [.\node at (0,-1.1) {C}; {\textit{xx}} ] 
    [.\node at (0,-1.1) {C}; {\textit{x}} ] ] 
    [.\textit{Reim}
    [.\textit{Nukleus}  [.C {\textit{x}} ]
    [.C {\textit{x}} ] ]
    [.\textit{Koda}         \node at (0,1) {C}; ] ] ]
    [.{\textbf{S}} 
    [.\textit{Onset} [.\node at (0,-1.1) {C}; {\textit{x}} ] ]
    [.\textit{Reim }    
    [.\textit{Nukleus} [.C {\textit{x}} ] ]
    [.\textit{Koda} \node at (0,1.1) {C}; \node at (0,1.1) {C}; ] ] ]
    ]
    \end{tikzpicture}
\end{frame}
\end{document}

Which gives me the desired result: