CDs mailed to us give us the most flexible options for including your material.  However, we need to have MP3 files encoded at 256kbit or higher if you are uploading material directly to us, or we are downloading material from you.  Variable Bit Rate [VBR] files will not suffice.  We are attempting to keep the overall volume output level within a certain range, which is very difficult with such a wide variety of sources.  We prefer mastered material, or live recorded material that has been normalized and thoroughly checked for clipping/peak-outs.  If you send us material we wish to include in the library and it does not meet the technical guidelines, we will contact you to arrange something.