Daniel Vik and Arturo Ragozini have just released a new version of PCM Encoder, a toolkit that allows you to encode WAV samples and playing them in crystal clear quality on MSX, using the standard PSG soundchip. Sample rates of 8kHz, 11.025kHz, 22.05kHz and even 44.1kHz are currently supported. The release package contains an encoder application (with source) and replayers so that you can use the resulting samples in your own productions.
You can listen to an example of a 44.1kHz sample played on a Philips VG-8020 MSX1 over here. For more information you can check out this forum thread or the extensive documentation included in the release package.
Relevant link: PCM Encoder