Essentially any sound file may be used. The actual recording process takes the audio from the headphones output of your computer, or other recording device with comparable output, and records it in the sound chip. This allows each user to work with files and applications they are familiar with.
Probably the most difficult and tedious task is to edit the sound to your liking. If you are planning on creating a loop then it becomes critical, for pleasing audio, to have the start and ending of the sound match closely. Any gross changes between the start and end will be noticed in the loop. Select an audio editing application and become familiar with it's tools. You will find that each sound is different and must be handled differently.
Once you have the sound you want it's time to record it to the sound chip. This is a monaural device. You will be recording from one channel only. Install your audio cable into the headphone output of your computer or suitable audio source. Select your playback program, such as Windows Media Player, and load your audio file. By all means use the applications with which you are most comfortable.
The record process involves enabling recording on the board and then initiating the audio file playback. The board will record until either the memory has been filled or recording is disabled. Depending upon the type of recording, loop or play once, you may want to modify the process by initiating the audio playback and then enable recording. This is something you will want to experiment with to find the best method for the sound involved as well as audio record levels. Having the recorder wired with a speaker and pushbutton you can play back each recording for review. The quality of the sound is directly related to the editing and recording settings. A little time and patience goes a long way towards a satisfactory sound.
The LED, D1, indicates when recording is active. It also will indicate the end of the recording, with a short flash, when in loop playback mode.