I'd like to introduce one of the songs in my music book first. In fact, It is a very popular song so that there's no need to explain about this.
What you have to highlight about the songs in music book is how they are developing like how the intro develops in Interlude?. If you played with the least amount of voicing in the intro, Interlude should be more voicing and Arpeggio in left-hand. Try to keep comparing those.
What's important today is that its the sound of Ti b IN FM7, which is 11th tension note. Chord tone refers to 1,3,5,7th note and these are the notes that make up the chord. Tension notes are 9,11,13 other notes. The way to fine them is that 9th note is the same as the 2nd note, the 11th note is the same as the 4th note, and the 13th note is the same as the 6th note.
For the sus4 chord, we use 1st, 4th, and 5th notes. If its a 7sus4 chord, use the notes of 1,4,5, and b7. The tension note is not used in the third chord, but the notes added to the seventh note are tension note. If it's from 3 to four, then it is a Sus4 chord. If you wrote 11 notes in addition to the 7th, it is a tension note. It is difficult, but try to give it a shot!
It's hard to find the tension 11th note in the major chord. As you see in the case of Sus4 chord, major 3 and 4 notes cannot be used together. It sounds like you do not want to hear so try to make sus4 chord with 4th note instead 3th. Tension 11th note is used in minor chord. If you add 11 note (=4 note) to the minor chord, it makes a very attractive sound.
For your information, if you want to use the 11th note of tension in a major chord, use #11th note.
Remember to use the 11th tension note for minor chord. Find the 4th note to find the 11th note. When you play FM7, the chord tone of FM7 is "Fa, Ra b, Do, Mi b." and If you add 11th tension note to this, it's "Sib." In this song, Fm7 has a lot of Ti b. Now do you understand everything? I used 11th note in the minor chord. This is why there's Mi b in Bbm7.
The fifth note is not so important in a chord tone, so we can skip 5th note but focus on 11th tension note or 13th note. Also you need to press 3 and 11th note to play the role of tension in the minor chord. If you do not hold the third note and press 11th note, it turns out to be sus4.