There are several sample packs on Brainstep’s SD card already, however you can also create your own.
You will need up to 12 different samples with a maximum total length of 2.7s
You can use a lower number of samples and just duplicate them to use all keyboard keys. If duplicated, samples will only be saved once to save space.
Brainstep’s samples are rather LO-FI: 8-bit mu-law encoded with a samplerate of 24kHz.
To convert your samples into Brainstep’s sample pack format, you can use the web-based converter tool. If you want to be able to do this without an internet connection, just right click on the link, press “save as”. The html file works without being online.