The following lessons become available when you complete the corresponding task. Only the first lesson under a specific difficulty setting will become available, more medals must be earned to unlock additional lessons.
Unlock Basic Guitar Lessons: Complete Rocker (stage 6-3) with at least 15 medals.
Unlock Technical Guitar Lessons: Complete Rocker 2 (stage 10-4) with at least 35 medals.
This is achievemd by getting a 'Perfect' rank on ALL 50 stages. To get a 'Perfect' rank on a song wait until it randomly becomes available as eligible for that rank. You will know when this happens because the frame for the stage will change colour and become wider and you have three attempts to get a 'Perfect' rank on that stage. If you are unsuccessful the 'Perfect' rank eligibility will disappear or switch to another stage.
If you fail a level 3 times the cafe will light up and you will get the option from the barista to skip the level. When you skip a level 'OK' will appear next to the level you skipped. This doesn't work for Remixes.
When you get 4 medals the telephone mini-game feature in 'Rhythm Toys' will become available. Dial the following codes during the telephone mini-game to unlock a hidden song from Rhythm Tengoku on the Game Boy Advance.
Unlock Song 1: Dial 5553282338 (found in Business Card under 'Rhythm Toys' - requires 1 medal).
Unlock Song 1: Dial 5557325937 (found in Tunnel Endless - requires 12 medals).
Unlock Song 1: Dial 5557268724 (found in Samurai Slice Endless - requires 17 medals).
Unlock Song 1: Dial 5557625688 (found in Battle Of The Bands - unlock by completing ALL 50 stages).