Rocksmith

This should unlock at 5,000,000 RSP (RockSmith Points). This can be unlocked in either Guitar or Bass career. The fastest way to earn points is by playing events. Note that you can always customize the setlist of the events, you do not have to play the default choices. Once you've gotten pretty good at a handful of songs, you can repeat them in multiple events. The better you are at the song, the more points you'll earn, and the faster you'll unlock these career achievements. On the other hand, trying new and different songs will add more variety to the game, and introduce you to different techniques. Your choice. You also earn RSP in practice, but only your highest practice score counts. For example, if you practice a song for the first time and score 50,000 points, you earn all 50,000 RSP. If you practice that same song a second time, and increase your score to 60,000 points, you earn only the 10,000 additional points in your career total. When you play events, however, you earn all the points you score, regardless of your prior scores. Thus, events are the fastest way to level up.

I unlocked this achievement on bass. I typically average between 40,000-90,000 points on most songs, occasionally topping 100k. So at my pace, it would have taken between 50-125 songs played to reach this level, if you want an idea of how long it takes to level up. Note, the next level up requires 7.5M RSP, a 2.5 million jump, so it does take longer to earn the top levels. Good luck and have fun.