Is it permissible to open another source of livelihood with money earned from selling songs, in order to abandon that activity, and does this money become lawful?

It is permissible for a poor person who has acquired unlawful money to take from it what suffices his needs and alleviates his poverty, such as his expenses, or a tool for a craft, or merchandise for trade. This money then becomes lawful for him, and he must dispose of what exceeds his needs.