You can create your own sounds that HyperCard can play.
Get a sound digitizing box from MacNifty and the program SoundCapΓäó, 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. Taper the end of the sound smoothly down to zero. (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.