commands for ritardando, rallentando, accelerando etc.

[Michael Kiermaier]

Hello!

I searched hard for a way to add a ritardando sign to my lilypond score.
The only way i found is to use the markup command.

I do not like it this way. It seems like a hack to me.
A ritardando appears quite often in sheet music, and for that reason I would 
like a \rit command (similar to \ppp) to automatically set the ritardando 
writing in the correct font, size and format. The same goes for 
"rallentando", "accelerando", "a tempo", the "poco a poco" completion, and 
probably some more.

For example, in LaTeX also exists a \sin command to get a sinus symbol, 
although it could be achieved via normal text commands, too.

Maybe I am blind and there already exist commands like these.

But if not:
Is there a reason that they do not exist? Will they be implemented in the 
future?
What do others think about this?

I am looking forward to your answers,

~michael