If a person is doing zabah and another person next to him says bismillah or if bismillah is being played on cd, will the animal which is being slaughtered (e.g. chicken) be halal?
No, it will not be halal. According to shariah, the Muslim person who is slaughtering should say Bismillah himself. In fact, the codex law defines halal in the similar way.
قَوْلُهُ وَالشَّرْطُ فِي التَّسْمِيَةِ هُوَ الذِّكْرُ الْخَالِصُ بِأَيِّ اسْمٍ كَانَ مَقْرُونًا بِصِفَةٍ كَاللَّهُ أَكْبَرُ أَوْ أَجَلُّ أَوْ أَعْظَمُ أَوْ لَا كَاَللَّهِ أَوْ الرَّحْمَنِ وَبِالتَّهْلِيلِ وَالتَّسْبِيحِ جَهِلَ التَّسْمِيَةَ أَوْ لَا بِالْعَرَبِيَّةِ أَوْ لَا وَلَوْ قَادِرًا عَلَيْهَا ، وَيُشْتَرَطُ كَوْنُهَا مِنْ الذَّابِحِ لَا مِنْ غَيْرِهِ هِنْدِيَّةٌ
Codex: 3.2 SLAUGHTERING
All lawful land animals should be slaughtered in compliance with the rules laid down in the Codex Recommended Code of Hygienic Practice for Fresh Meat1 and the following requirements:
3.2.1 The person should be a Muslim who is mentally sound and knowledgeable of the Islamic slaughtering procedures.
3.2.2 The animal to be slaughtered should be lawful according to Islamic law.
3.2.3 The animal to be slaughtered should be alive or deemed to be alive at the time of slaughtering.
3.2.4 The phrase “Bismillah” (In the Name of Allah) should be invoked immediately before the slaughter of each animal.