Feature request: syntax change of metronome markings

[Juergen Reuter]

Hi, there!

It would be nice, if the metronome marking syntax would allow extensions 
for greater flexibility in future versions of lily.  For that purpose I 
would like to make a request for the following syntax change:

\tempo duration = per-minute

should become

\tempo duration = duration

with the special case that the right-hand "duration" may be specified 
absolutely as bpm:

\tempo duration = \bpm per-minute

That is, instead of writing

\tempo 8.=120

you would say:

\tempo 8.=\bpm 120


This way, in future versions of lily, the syntax would be open to be 
extended for allowing constructs like:

\tempo 4.=4

which means that the tempo changes such that the former duration of a 
quarter note is now equal to that of a quarter+eigth note.  This is a 
quite typical example e.g. when changing the meter from 4/4 to 6/8.

Greetings,
Jürgen