I have a simple DIY lo-fi microphone on the pine tree in front of our house:

I record 20 sec long samples with it, every 4th hour. Then these wav files get mixed together to produce a 2 minute long output which I can use as a background sound under my automatic webcam timelapse videos.

Audio recording is done with sound-recorder, further processing is with sox in three steps:

• fading & padding: the end of the first file gets a fadeout, the beginning of the last file gets a fadein, other files get both fadeins and outs, then every file gets a silence in the beginning, length is calculated using: (filenum-1)*($lengt
  h-5)
• mixing: the first file gets mixed with the second, then this mix gets mixed with the third file and so on, they will be mixed together because of the previously applied padding
• normalizing, compressing and fading: after normalizing and compressing, it applies fadein to the beginning and fadeout to the end of the whole file

I’m using these scripts. webcam-recordsound is the cron file, you have to put it under /etc/cron.d, recordsounds start recording of a 20 sec long wav file, mixsounds mixes the recordings together and applies (audio) compression on them. common.sh contains the log function which I use in the scripts.