Musicians often develop a high capacity for keeping musical information in their memories, both short-term and long term. The most basic type of musical memory is called pitch memory. To give a simple example, when you play a tone on a pitch pipe in order to establish the key before singing a song, you are using your short-term pitch memory in order to store the starting tone in your mind before you start singing. In addition, if the song starts on a tone other than the "one" of the key, you must use your relative pitch skills to find and store the starting tone of the song.
With practice, most of this becomes automatic and is done without any conscious effort. Sometimes, you will need to keep a tone in your mind as other music is playing. You may also find that you need to translate a melody to your instrument that is sung or played on a different instrument. In these cases you must be able to distinguish and store the tonal information (that is the pitches used in the melody), independent of the instrument sound. The development of a strong memory for pitch regardless of timbre (instrument sound) is one of the first steps in building your general musical memory.
Tonal Recall will strengthen both your pitch memory and your relative pitch skills.