Inspired by The largest vocabulary in hip hop, I wanted to do a similar analysis across a more generalised list of musicians. I stumbled across this List of best-selling music artists and decided to dig deeper. The list is large enough (99 musicians and 25 genres) for the analysis to be interesting and small enough to not require complicated analysis techniques. Combining this with data from the Musixmatch database leads to the following analysis.

To start with, these are the 93 musicians1 from that list sorted by genre :
1 Bruce Springsteen, Chicago, Def Leppard, Journey, The Beach Boys and The Doors from the original list of 99 musicians don’t grant permission to Musixmatch to use their lyrics. Therefore, they couldn't be included in the analysis.
The aim is to compare the vocabulary size of these musicians. Some of them have released a lot more songs than the others because of the sheer longevity of their career and how prolific they are. Top Bottom Artists
To prevent the analysis from being skewed purely by the number of songs released, the vocabularies are compared across the 100 densest songs (by total number of words) that they have released. Only 6 of these musicians have released less than 100 songs, so it is a good threshold. Also, 100 songs comprises 8 to 10 albums of music which would span at least 5 to 10 years of work. This should give a fair idea of the overall vocabulary of these musicians.

Here are some definitions you should be acquainted with

VOCABULARY SIZE The number of unique words (across any language) used by a musician in 100 (or less) densest songs across their career.

LYRICAL DENSITY The total number of words (across any language) used by a musician in 100 (or less) densest songs across their career.

NEW WORD INTERVAL (N.W.I) On average, the number of words after which a new word is used by the musician. This is the ratio of (Lyrical density / Vocabulary Size). An N.W.I of X means every Xth word in the lyrics of the artist is a new word, that is, a word he/she has never used before in any of his earlier songs.
Calculated over the 100 (or less) of their lengthiest songs
Clicking an artist plays the Spotify preview of their most popular song
Musicians There are 4 rappers in the list and they are at the top of the vocabulary chart. Amongst them, Eminem leads Jay-z, 2Pac, Kanye West and The Black Eyed Peas by a big margin. Eminem also has the overall highest words per song ratio of 1018.5.
Freewheelin' Given how articulate and descriptive his songs are, it is no wonder Bob Dylan ranks so highly. He also ranks at the top (#11) of the N.W.I ranking (on average he uses a new word after writing 9 words).
These superstars have released songs in multiple popular languages. Their vocabularies in different languages are getting summed up leading to a high overall vocabulary size. This was a result I was not expecting when I started the analysis.
Celine Dion I had not expected a pop sensation like her to rank high since they rely on simplicity to get their message across. It lays bare my ignorance of her music. Also, she is the only one who ranks in the top 15 by vocabulary size as well as the total certified album sales.
Not the least
Kenny G
Whoever said songs can’t sell without lyrics.
The average vocabulary size across all the musicians is 2677 words. Around 40 musicians have a vocabulary size within 400 words of the average . Get your song-writing vocabulary size in this range to be a top selling artist.
Keep it simple The three top selling musicians of all time rank low in the vocabulary chart. No wonder the simplicity of their lyrics breaks the barriers of geography, age, language and they are admired globally. Conversely, Mariah Carey ranks high in both the charts (#9 in the sales chart and #20 in the vocabulary chart).
The following chart shows the average vocabulary size of artists in different genres. In the parantheses is the number of artists in the list that sing in that genre. Since our list includes only 93 artists, it is not a very good generalization.
Calculated for the top selling artists as per the Wikipedia article. ( ) denotes number of artists analyzed in that genre
Some simple insights can still be taken. Hip-Hop is way ahead of the other genres (d’oh). Folk comes in second but since there is only one folk artist (Bob Dylan) in the analysis it is not representative at all. Pop is the genre with the most number of musicians and its average vocabulary size (2464 words) is close to the average vocabulary size across all artists (2677 words). Same thing applies to the Rock genre as well.
There is a large variation of vocabulary size in the 93 top selling musicians and there is no overall correlation between the commercial success of a musician and their vocabulary size.

This analysis should not be interpreted as saying that one musician is better than the other, it is just another insight into the work of these amazing artists. It gives us a peek into the minds of different songwriters, some tear your heart with just a few words while others paint an intricate picture with a thousand words. Quoting John Lennon out of context explains this songwriter dilemma quite well -
“Half of what i say is meaningless, but I say it just to reach you” - Julia, White Album
All the lyrics data and other metadata (images, album lists, track lists, etc) is extracted using the Musixmatch API. Python is used for fetching the data and analyzing the lyrics. The analysis could be improved to remove coincidental sounds (ooh, aah, etc) and other such words which are not part of a dictionary. The data and the code will be released if anyone is interested.

The largest vocabulary in hip hop compares the vocabulary of various musicians across the first 35000 words written by them. Instead of constraining by the number of words we used the 100 densest songs. Just out of curiosity (and for the sake of completeness) we used the same methodology by considering 10000 words written by each artist. The results of the two approaches don’t differ too much, the top 5 ranked musicians remain the same. The top 10 ranked musicians are the same with a slight shuffling of the ranks. Andrea Bocelli moves from #8 to #6, while Black Eyed Peas move from rank #6 to #7 and Julio Iglesias from #7 to #8. No significant changes are observed on the whole (more details). Thus, we used 100 songs as the constraint since it makes more sense intuitively and musically.