Read the manual of Meloditronic PhoenixStudio, a Rebirth-like synthesizer/sequencer for a Windows Mobile based phone or PDA by Henrik Rydgard. It works on Windows Mobile 6.5 or lower (like WinCE 2002, 2003). Development on the app has stopped in 2004 and the meloditronic.com website has been discontinued.
PhoenixStudio is now free software. Download PhoenixStudio.
And there is also an Android version of PhoenixStudio.
You can also download Phoenixstudio WavExporter.zip (500KB). A Windows based program to convert your .pnx files into cd-quality wave-files. Make sure you run it in Compatibility Mode for XP SP3. Also, after you have pressed the "Export Loop to WAV" button, be quick to enter a file name and press Save. The program has a tendency to crash when you wait for too long.
Also: when you have used your home-made drumsamples in a song, make sure you also place these samples in exactly the same WavExporter directories and all will work out fine.