Using and listening to musical instruments is Haram, based on many evidence, of which is Allah's Statement, (Part No. 26; Page No. 248)
Help you one another in Al-Birr and At-Taqwâ (virtue, righteousness and piety); but do not help one another in sin and transgression. And fear Allâh. Verily, Allâh is Severe in punishment.
The Prophet (peace be upon him) stated,
Verily, among my Ummah (nation based on one creed) there will be people who will deem as lawful: Zina (sexual intercourse outside marriage), silk [for men], Khamr (intoxicants) and musical instruments.
There are many other evidences. Playing music is included in the prohibition of musical instruments mentioned in the Hadith. It is considered cooperating in sin and transgression, as your work induces people to drink Khamr. Accordingly, those who advised you to quit this work are right. You must give up your job at once, repent to Allah, and seek His Forgiveness. Allah will compensate you with better lawful means of income. It was authentically reported that the Prophet (peace be upon him) stated,
Whoever abandons something for the sake of Allah, Allah will replace it with something better than it.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.