>>32095612Audiofile Polka here.
Streaming services usually remix or alter the original track to fit a certain file size to conserve bandwidth. Depending on the compression algorithm, it does weird things to the track. There may also be further compression done to the stream depending on the app you are streaming it from and the hardware you use. All of this compression will cause the track loose fidelity or lose separation in different frequency ranges. This is why you want to buy the audio CD and get a lossless copy of the track, assuming they took it straight from the master track unaltered.
Usually most people will not notice this difference if their ears are untrained. This usually happens because of low fidelity sources like iphones, onboard audio, or using normi headphones. But Polkas with good ears can tell the difference.
Surprisingly, the youtube MVs from Polka have pretty high quality audio. If you want to experience the best quality of Polka I suggest you try listening to them with Fubar2000, using the youtube plugin, with the WASAPI plugin and switching the audio output to use WASAPI. This will bypasses any audio compression caused by your browser, app, or operating system.