Here are the completed sentences using the correct forms of the adjectives:

1. Some people think that Music isn't **as important** as Maths or Science. I don't agree.

2. The guitar is one of the **most popular** instruments around.

3. It's **easier** to play an instrument after you've been practising for a while.

4. I play the piano **better** than I play the violin.

5. Guitars aren't **more expensive** than many other instruments.

6. Saxophones are **heavier** than a lot of instruments.

7. Traditional pianos are **more suitable** than keyboards for beginners.

8. Masi is the **best** singer in our class.

For section VII, here's the response:

Avril Lavigne is one of the **most famous** musicians to come from Canada. She became **the youngest** female to go to the top of the UK album charts in January 2013. She was aged 18 years and 106 days.

But Avril wasn't **more young** as young as singer Stevie Wonder. He was only 12 years old when he reached the top of the US chart in 1963.

In 1988, Red Hot Chili Peppers became **the fastest** (or **faster**) rap band. In 2005, he rapped again and became the **quickest** rapper than before! He rapped 63 syllables in 25 seconds.

Britney Spears became **bigger** than **the biggest** selling entertainer in December 2001 when her sales reached 31 million records.

Let me know if you need any more help!