In 5719 (1959), R. Moshe Feinstein was asked to rule on
the permissibility of playing the music of a certain songwriter

who was rumored to engage in disreputable behavior.
(Teshuvot Iggerot Moshe, Even Ha-Ezer, I, no. 96.)

Feinstein distinguished between this composer’s early compositions and his later ones.
Any music written in his early years when this individual comported himself appropriately
remained permissible; at that time he behaved properly
and his later activities can not retroactively taint his prior achievements.

One of the proofs that R. Feinstein brought is
from the case of a Torah scroll that was written by a heretic
—Jewish law requires that such a scroll be destroyed so as not to perpetuate his name, reputation or achievements. (Hil. Sefer Torah 6:8)

However, the law also asserts that
a scroll written while that person was a true believer remains valid, even if he later became an apostate.
(Pit’hei Teshuvah, Yoreh De’ah 281, no. 2.)

Concerning subsequent musical compositions,
R. Feinstein stated that even those songs that this person wrote
after his “reputation became objectionable”
are permissible because music, unlike Torah scrolls,
have no intrinsic holiness.

Furthermore, the questionable activities
had nothing to do with undermining the fundamentals of Jewish belief but rather with casualness with regard to the intermingling of the sexes that were not in keeping with Orthodox norms.
Such a lapse would not render a Torah Scroll he wrote invalid;
it would certainly not disqualify his music.
R. Feinstein wrote nothing about learning Torah from this individual.

However, based on R. Feinstein’s discussion,
one might distinguish between the teachings and insights
of a heretic before and after his apostasy:
the earlier Torah would remain "kosher";
the latter Torah would be banned.