package net.choccy.darksteel.item.custom;


import net.minecraft.sounds.SoundEvents;
import net.minecraft.sounds.SoundSource;
import net.minecraft.world.InteractionHand;
import net.minecraft.world.InteractionResultHolder;
import net.minecraft.world.effect.MobEffectInstance;
import net.minecraft.world.effect.MobEffects;
import net.minecraft.world.entity.player.Player;
import net.minecraft.world.item.Item;
import net.minecraft.world.item.ItemStack;
import net.minecraft.world.level.Level;

public class DarksteelHornItem extends Item {
    public DarksteelHornItem(Properties properties) {
        super(properties);
    }

    @Override
    public InteractionResultHolder<ItemStack> use(Level level, Player player, InteractionHand hand) {
        if (!level.isClientSide()) {
            player.addEffect(new MobEffectInstance(MobEffects.DAMAGE_BOOST, 200, 4));
            level.playSound(player, player.getX(), player.getY(), player.getZ(), SoundEvents.RAID_HORN, SoundSource.PLAYERS, 1.0F, 1.0F);
            player.getCooldowns().addCooldown(this, 400);
      	}
        return super.use(level, player, hand);
    }
}

This is the code. The strength and cooldown work, but the sound does not play. Anyone know why?

Move your level.playsound() outside the if statement, it shouldn't be fired on the serverside.