However, we can say that:
* He has released multiple albums: His music career spans several decades with albums like "Has Been" (2004), "Seeking Major Tom" (2011), and "Ponder the Mystery" (2018).
* His music gained some attention: His unique vocal style and choice of material generated media buzz, particularly with his 2011 album "Seeking Major Tom" which included a cover of David Bowie's iconic song.
* He has a dedicated fanbase: While his music might not be mainstream, he has a loyal following of fans who enjoy his music and his comedic approach to it.
While exact sales figures are unavailable, it's safe to say that William Shatner's music has achieved a level of success, even if it's not comparable to chart-topping artists.