I am happy to share my music,see[dickmilesmusicyoutube]and also my website, www dickmiles.com.
I do think it is good manners to ask first or even afterwards.
a few years ago it would have been customary if another musician had a tune, to ask the musician can you teach me it,speaking for myself I have never refused,
now someone can tape you on a mobile phone and learn the tune without asking.I think this attitude shows contempt,.[cant be bothered with the player, just want the tune]
when I learned tunes off a traditional fiddler friend of mine,part of the learning of the tunes was the friendship I built up with him.
learning about his life,learning how he came to learn the tunes himself,learning about local musical history etc.I would never have dreamed of recording him without his permission,in fact he explicitly said to me that I wasnt to let anyone else hear the recording[because he didnt think he played as well as he used to].
IMO if people are interested and respect music they should also be interested in AND respect the carrier.,they are likely to learn far more as well,the musiciamn might say well sometimes I dont play it like that ,but I do an ornament somewhere else ETC .