Although there have been different storage mediums used for saving sound waves (physical scratches on a record, magnetic signals, etc) the most popular professional analog storage medium was Magnetic Recording Tape, made with a layer of sensitive magnetic particles glued to a plastic strip.  As will be discussed later in the course, although this medium was considered the peak of Analog storage, it eventually became less used when Digital storage (and eventually processing and sound manipulation) was introduced.

Magnetic tape machines were aligned in ways that would strengthen the magnetic signals being put on the tape enough for maximum sound quality without bleeding into adjacent tracks.  Machines were also aligned for optimal sound for each type of tape (and signal strength) used.  When aligning a tape machine, you use a tape with pre-recorded frequencies (low, middle and high) at a specific strength or magnetic density (measured in nanowebers per meter).

Magnetic tape does produce hiss as a byproduct that can be heard during quiet moments where there are no louder sounds to cover.  Ways to get around the hiss included recording techniques that took advantage of optimal tape recording levels by squeezing loud parts and boosting soft parts, or devices that reduced the amount of hiss heard during sound playback. One such system was Dolby, which would overly boost the high frequencies during recording and then expand the sound and reduce the extra high frequencies during playback.  The reduction of high frequencies also reduced the hiss from the tape.

These days most sound is stored using DIGITAL technology, which involves converting sound into digital computer information that can be stored on any hard drive. Where once I received material to mix on large reels now I receive hard drives, USB thumb drives, FTP file transfer, "Dropbox", or even huge emails.