Gnumeric is a spreadsheed app like excel and available for linux, windows and as source code.
http://www.gnome.org/projects/gnumeric/I use it like this:
- you got an unknown loop...
- you make a test track with length 1 bar
- you start playback and alter the song tempo and sample fine tune to match one bar of the loop. You now know the original tempo given as #note, #temp and #speed.
- after that you can use the loop in your arrangement, calculating any #note and #finetune values to match your song tempo. A value of 403,78 eg. means four halftones up + 3,78 cents (sample finetune of aprx. +4).
Does that answer your question?
Edit: if speed is set to 6 and basenote set to C-4 the file will play at 'real world timing', IMHO. But I might be wrong on that one.