You can create your own sounds that WildCard can play.
Get a sound digitizing box from MacNifty and the program SoundCap, also from MacNifty.
Record your sounds on a tape recorder. Connect the tape recorder to the MacNifty digitizer and run SoundCap (see its instructions). Choose a sampling ratio of 2 for music or 3 for speech from the Choices menu. Edit your sounds to cut off any extra. (Do not choose Data Compression in the File menu.) Save your sound in a file.
To convert a SoundCap file into a resource (of type 'snd ') for HyperCard, use the HyperTalk command SoundCapToRes.