transcoding recipe request

[Louis-David Mitterrand]

Hello,

I have a directory tree of sound files in .flac format and I am trying 
to build a makefile to convert all these files to other formats (ogg, 
alaw, mp3, etc.) in a similar, parallel directory tree. 

This is what I have:

/home/ldm/music/flac/classical/opera/author1/*.flac
/home/ldm/music/flac/jazz/author2/*.flac
/home/ldm/music/flac/rock/author2/*.flac
etc...

and this is what I'd like the makefile to auto-generate:

/home/ldm/music/alaw/classical/opera/author1/*.alaw
/home/ldm/music/alaw/jazz/author2/*.alaw
/home/ldm/music/alaw/rock/author2/*.alaw
etc...

(the directory tree has a variable depth)

Here is the rule I wrote to convert the files:

%.al: %.flac 
    flac -cds $< | sox -S -t wav - -r 8000 -c 1 $@ resample -ql
    mv $@ alaw

What I need is a way of:

- recursing into the flac directory tree, 
- generate a target list from the flac files with patsubst
- another way?


Thanks in advance for your suggestions,