exercise!

The same way guitarist improve by playing

back in the 60's/70's we recorded and sold an exercise tape for musical instruments based on the well know fact that a guitar etc. can be "aged" in tone by placing it in front of speakers playing at a "REASONABLE" volume. the tape expanded on this by including present tones that repeated at various speeds throughout the recording - it worked quite well and many tapes were sold - might just re-do it on CD!!

Pete