It is sometimes desireable to combine multiple GCF files into a single file. This can be achieved using only operating-system command-line tools.

GCF files are strings of self-contained 1k data blocks with no additional header or trailer information so, under Linux, it is sufficient to

 cat a.gcf b.gcf [c.gcf ...] > all.gcf 

Under Windows, problems can arise with the copy command if there are any end-of-file characters (0x1A / ^Z) in the data, so you need to use an explicit binary copy:

copy /b a.gcf + b.gcf + c.gcf all.gcf 

These techniques work with any GCF files, regardless of the number of instruments, streams, time periods, etc.