Thanks for that. I don't have any way to post images so Im about to send some of you a small email with a screen shot attached. I was lucky enough to find a recording from December last year of the same midi file so the screenshot shows current waveform to the left and last years waveform to the right.

I agree that real instruments are non-symmetrical but I think I'm well outside that amount of variation!

I'll have a chance to investigate further on Sunday (UK).

Re "How can a level in a MIDI file be excessive" you can get signal clipping caused by the way the channels of a file are mixed digitally within a keyboard.

The digital mixing takes the instantaneous value of each voice waveform, scales it by the mix level for the track, adds up all the resulting values and arrives at a total instantaneous value for the waveform. If this value is larger than the maximum possible value for the summed waveform then the value will effectively get clipped at that maximum.

This is not a fault as such but a consequence of the way the maths is done, in some ways it's the computing equivalent of gain structures.

As a result of this, on my 3k, I rarely set individual track levels above 70, especially drum or bass tracks as these are the ones that are most likely to overload the system.

[This message has been edited by MacAllcock (edited 01-21-2010).]

[This message has been edited by MacAllcock (edited 01-22-2010).]

[This message has been edited by MacAllcock (edited 01-22-2010).]