The custom soundfeature was never ment as a downloadbase..it's for random sounds and the possibility to send your contact small sounds (you can record your own: click add new sound and choose whatever you like to do).
What you could do is make a .plp (open soundlibrary > add new sounds > export existing sounds to create a new soundpack..then follow instructions, pretty selfexplanatory). After you've done that you can send the .plp to your friends or upload your soundpack to the
Plus! soundpack DB (you can download Plus! soundpacks from there without registering and upload after registering). That way your friends can download your soundpack, next they can convert the sounds within the soundpack to separe mp3 files with the Soundpack extractor attached
here, if they wish to hear the sounds before adding them to their own Plus! soundlibrary
Same goes for you ofcourse, there already are several soundpacks available for download
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