Well, let me start off. It must be under 1 minute.
It doesn't have to be shorter than 1 minute, but it has to be under 1 MB/1024 KB for blockland to take it, and Badspot and players that'll have to download it from the server would prefer the loops being under 500 KB.
OP you have these options, shorten the loop, reduce the bit rate, and/or reduce the sampling rate to 32 KHZ (32000 hz). Considering that the loop is 15 minutes long, you really want to short this by a ton, and make it a mono loop too...removing that alone cuts the file size by 50%.
It won't work in Blockland since it's stereo and 13.8 MB in size, so you need to make it under 1024 KB/1 MB and mono (one audio channel only) for it to actually work in blockland, and that means cutting the loop, reducing bit rate to a reasonable amount since quality will stay pretty good up until a certain point, and reducing the sampling rate to 32,000 hz, which would have almost no effect on audible quality and reduce the file size by a good amount of the time.
