使用命令行工具合并两个音频文件

I've to merge two (or more) audio files (like a guitar and a drum track) into a single file. I'm running over linux CentOS and I'd need a command line tool to do so, because I've got to run this as part of a background process, triggered via crontab of a custom bash script. I also need to be able to change the pan, volume, trim and start time (i.e I want the guitar track to start after 1.25ms after the drum track so that they can be both in sync with each other).I've to merge two (or more) audio files (like a