First, you have to make sure that all the files have a .Aiff or .wav extension in their name.

You will be able to see files with a name like on Cowbell on the Smart Media card when in the Mac, but when you put the card in Motif and select waveform they will not appear. Motif needs to see the extension .aiff/.aif or .wav in the name to recognize these files.

You need to add the proper extension. So rename the files on your Mac and add the aiff or .wav extension (in our example-cowbell.aiff) . This should solve the problem.