Well, here’s your answer. This article is somewhat spoilerific. While it doesn’t tell you how to solve any specific puzzle, the information it contains is derived from puzzles I’ve solved in the past. I’ve tried to supply enough hints to get moving in the right direction without totally spoiling any particular puzzle.

Solving a music puzzle requires some understanding of music theory, which is the study of the language and the notation of music. Musical notation is any system which uses written symbols to represent aurally perceived music. Many types of notation systems have been created throughout history, but most written music you are likely to encounter will use only  modern musical symbols.

The topic of music theory is vast – far too big to include in a single article here. But the links presented so far will take you to a great set of resources to understand how music works so that you can get started in cracking puzzles that use music.

Here are just a few of the many possible ways in which music could be used to conceal information (such as a secret message or the coordinates of a geocache):

Note Names

Notes have letter names, from A to G. A puzzle constructor might begin with a word that uses only those letters, such as BAG, ACE, BADGE, or CABBAGE, then replace each letter in the word with a corresponding note.

Intervals

An interval is the difference in pitch between two notes, played either at the same time or played successively. An interval of a single half step is called a minor second, two half steps is a major second, three half steps is minor third, and so forth. A puzzle constructor might encode a series of numbers as a series of intervals.

Rhythms

A beat is a pulse that constitutes the fundamental unit of time in a piece of music. A measure is a segment of time, and the number and note value of beats in a measure is called the time signature. For instance, a measure of four beats in which a quarter note gets the beat is said to be in 4/4 time. A measure of six beats in which an eight note gets the beat is said to be in 6/8 time. Patterns of beats can be used to encode just about any kind of information, including letters, numbers, symbols, and more.

That should be enough to get you going. Good luck!

The result of this effort is the Puzzle Solving 101 Series of geocaches. Each cache in the series offers a lesson on a particular topic of puzzle solving. The description of each cache offers a description of the topic as well as solving tips. Each lesson also contains an example to solve using the tips presented in the lesson – the solution to each example puzzle is the location of a geocache in Broward County, Florida.