DLS is an audio file format used by Roland. DLS stands for “DownLoadable Sound,” and hold sounds that can played back using a MIDI input device. DLS files are constructed using the Interactive Music Architecture, and can be opened using programs such as Simple Synth. DLS files are similar to .DLP files, which are also constructed with IMA.
Learn more about .DLS files:
Search on IT Knowledge Exchange for .DLS-related questions.