How sound is it that the prayers, supplications, recitation of Quran, fasting, and Zakat of one who works for a company that produces and distributes cassette tapes (songs - Quran) are not accepted by Allah?

Congratulations on your repentance and your diligence in prayer. These are great blessings and the pillar of faith. The words of whoever claims that your prayer and supplication are not accepted are incorrect. For Allah accepts sincere acts of obedience and those that follow the Sunnah (definition), even if the one performing them commits sins. We advise you to seek lawful employment other than selling haram (definition) music tapes. And whoever fears Allah – He will make for him a way out and provide for him from where he does not expect.