This chapter covers MMA filenames, extensions and a variety of commands and/or directives which effect the way in which files are read and processed.
But, first a few comments on the location of the MMA Python modules.
The Python language (which was used to write MMA) has a very useful feature: it can include other files and refer to functions and data defined in these files. A large number of these files or modules are included in every Python distribution. The program MMA consists of a short ``main'' program and several ``module'' files. Without these additional modules MMA will not work.
The only sticky problem in a program intended for a wider audience is where to place these modules. We've decided that they should be in one of three locations:
If, when initializing itself, MMA cannot find one of the above directories, it will terminate with an error message.
For most files the use of a the filename extension ``.mma'' is optional. However, we suggest that most files (with the exceptions listed below) have the extension present. It makes it much easier to identify MMA song and library files and to do selective processing on these files.
In processing an input song file MMA can encounter several different types of input files. For all files, the initial search is done by adding the filename extension ``.mma'' to filename (unless it is already present), then a search for the file as given is done.
For files included with the Use directive, the directory set with setLibPath is first checked, followed by the current directory.
For files included with the Include directive, the directory set with setIncPath is first checked, followed by the current directory.
Following is a summary of the different files supported:
One further point to remember is that filenames specified on the command line are subject to wildcard expansion via the shell you are using.
Normally, a file is processed until its end. However, you can short-circuit this behavior with the Eof directive. If MMA finds a line starting with Eof no further processing will be done on that file ... it's just as if the real end of file was encountered. Anything on the same line, after the Eof is also discarded.
You may find this handy if you want to test process only a part of a file, or if you making large edits to a library file. It is often used to quit when using the Label and Goto directives to simulate constructs like D.C. al Coda, etc.
The search for library files can be set with the LibPath variable. To set LibPath:
SetLibPath PATH |
You can have only one path in the SetLibPath directive.
When MMA starts up it sets the library path to the first valid directory in the list:
The last choice lets you run MMA directly from the distribution directory.
You are free to change this to any other location in a RCFile ().
The LibPath is used by the routine which auto-loads grooves from the library, and the Use directive. The -g command line option is used to maintain the library database ().
You can include a leading `` /'' in the path. In this case the path will be expanded to a complete pathname.
MIDI file generation is to an automatically generated filename (). If the OutPath variable is set, that value will be prepended to the output filename. To set the value:
SetOutPath PATH |
Just make sure that ``PATH'' is a simple pathname with no spaces in it. The variable is case sensitive (assuming that your operating system supports case sensitive filenames). This is a common directive in a RC file (). By default, it has no value.
You can disable the OutPath variable by not using an argument in the SetOutPath directive.
The PATH used in this command is processed though the Python os.path.expanduser() library routine, so it is permissible to include a leading ``~'' in the name (which expands, on Unix and Linux systems, to the name of the user's home directory).
If the name set by this command begins with a ``.'', ``/'' or `` \'' it is prepended to the complete filename specified on the command line. For example, if you have the input filename test.mma and the output path is ~/mids--the output file will be /home/bob/mids/test.mid.
If the name doesn't start with the special characters noted in the preceeding paragraph the contents of the path will be inserted before the filename portion of the input filename. Again, an example: the input filename is mma/rock/crying and the output path is ``midi''--the output file will be mma/rock/midi/crying.mid.
Other files with sequence, pattern or music data can be included at any point in your input file. There is no limit to the level of includes.
Include Filename |
A search for the file is done in the IncPath directory (see below) and the current directory. The ``.mma'' filename extension is optional.
The use of this command should be quite rare in user files. We use it extensively in our library files to include standard patterns.
The search for include files can be set with the IncPath variable. To set IncPath:
SetIncPath PATH |
You can have only one path in the SetIncPath directive.
When MMA initializes it sets the include path to first found directory in:
The last location lets you run MMA from the distribution directory.
If this value is not appropriate for your system, you are free to change it in a RC File. You can include a leading `` /'' in the path. In this case the path will be expanded to a complete pathname.
Similar to Include, but a bit more useful. The Use command is used to include library files and their predefined grooves.
Compared to Include, Use has important features:
Let's examine each feature in a bit more detail.
When a Use directive is issued, eg:
use stdlib/swing |
MMA first attempts to locate the file ``stdlib/swing'' in the directory specified by LibPath or the current directory. As mentioned above, MMA automatically added the ``.mma'' extension to the file and checks for the non-extension filename if that can't be found.
If things aren't working out quite right, check to see if the filename is correct. Problems you can encounter include:
As mentioned above, the current state of the compiler is saved during a Use. MMA accomplishes this by issuing a slightly modified DefGroove and Groove command before and after the reading of the file. Please note that Include doesn't do this. But, don't let this feature fool you--since the effects of defining grooves are cumulative you really should have SeqClear statements at the top of all your library files. If you don't you'll end up with unwanted tracks in the grooves you are defining.
In most cases you will not need to use the Use directive in your music files. If you have properly installed MMA and keep the MMADIR files up-to-date by using the command:
mma -g |
grooves from library files will be automatically found and loaded. Internally, the Use directive is used, so existing states are saved.
If you are developing new or alternate library files you will find the Use directive handy.
If you wish to process a certain file or files before your main input file, set the MmaStart filename in an RCFile. For example, we have a number of files in a directory which we wish certain Pan settings. In that directory, we have a file mmarc which contains the following command:
MmaStart setpan |
The actual file setpan has the following directives:
Bass Pan 0 |
So, before each file in that directory is processed, the Pan for the bass and walking bass voices are set to the left channel.
If the file specified by a MmaStart directive does not exist a warning message will be printed (this is not an error).
Also useful is the ability to include a generic file with all the MIDI files you create. For example, we like to have a MIDI reset at the start of our files, so we have the following in our mmarc file:
MMAstart reset |
This includes the file reset.mma located in the ``includes'' directory ().
Because it is not uncommon to have multiple mmarc files, each with a different MMAstart directive, the files are appended to the existing list. Each file will be processed in the order it is declared. You can have multiple filenames on a MMAstart line.
Just the opposite of MmaStart, this command specifies a file to be included at the end of a main input file. See our comments above for more details.
To continue our example, in our mmarc file we have:
MmaEnd nopan |
and in the file nopan we have:
Bass Pan 64 |
If the file specified by a MmaEnd directive does not exist a warning message will be printed (this is not an error).
Because it is not uncommon to have multiple mmarc files, each with a different MMAend directive, the files are appended to the existing list. Each file will be processed in the order it is declared. You can have multiple filenames on a MMAend line.
When MMA starts it checks for initialization files. Only the first found file is processed.
The following files are checked (in order):
All found files will be processed.
Note that the second file is an ``invisible'' file due to the leading ``.'' in the filename.
By default, no rc files are installed.
The rc file is processed as a MMA input file. As such, it can contain anything a normal input file can, including music commands. However, we suggest you limit the contents of your RC files to things like:
SetOutPath |
A useful setup is to have your source files in one directory and MIDI files saved into a different directory. Having the file mmarc in the directory with the source files permits setting OutPath to the MIDI path.
Included in this distribution are a number of predefined patterns, sequences and grooves. They are in different files in the ``lib'' directory.
The library files should be self-documenting. A list of standard file and the grooves they define is included in the separate document, supplied in this distribution as ``mma-lib.ps''.