Rumbar Pirates

The Rumbar Pirates are a long dead pirate crew from the West Blue. They were first mentioned by Crocus as the group of pirates who brought Laboon to the Twin Capes.

Travels in the West Blue
During their travels in the West Blue they found a baby whale following them. Seeing he was alone and sad they decided to play music to/for him, in order to cheer him up. The next day they thought he was gone but they found him again. Seeing he still followed them they decided to play for him again and this time allowed him to follow them seeing how cute he was. While feeding him some bait it was revealed that Brook had named him Laboon.

The Promise
During a fierce fight with enemy pirates, several crewmembers fell into the sea, none of which could be saved. It was at this time the baby whale helped them. While spending time with Laboon some of the crewmembers thought he liked Brook the musician because they were near-identical (Brook's afro made him look like a whale). Before the Rumbar Pirates ventured into the Grand Line, fifty years ago, they decided it was no place for Laboon; even if he was an adult he wouldn't even compare to the monsters in the Grand Line. By the orders of the captain they were to ignore him hoping he would go away. At the entrance they befriended the lighthouse caretaker Crocus who pointed out that Laboon had followed them asking if it was their pet, to everyone's shock. They decided to stay for some time. After three months time of repairs to their ship and resupplying, the crew finally decided to move on. After making an agreement with Crocus to take care of Laboon, while they were gone, all crew members made their farewell to Laboon, with a promise to return in a few years' time after sailing all the way around the Grand Line.

Venturing the Grand Line
However their return was not to be. They traveled far into the Grand Line, experiencing its cruel sea and unpredictable weather, eventually sailing into the Florian Triangle. At that point had Yorki, their captain, and several of the crewmembers attracted an incurable disease. Deciding no more should be infected Yorki traveled away with the sick crewmembers and hoped to pass through the Calm Belt. It was at that point most of them died, which was later reported and led Crocus to believe that they had become scared and left through the Calm Belt.

Florian Triangle
Despite losing half of the crew, the remaining Rumbar Pirates continued sailing through the Grand Line on a new ship with Brook as their captain. As they traveled through the sea, Brook gained a bounty for himself, and things at first went smoothly for the remaining Rumbar Pirates. However, upon entering the Florian Triangle, Brook and his remaining crewmates were attacked by some enemy pirates. A good number of the crew survived the attack, albeit barely, but since the enemy had tainted their weapons with poison and the Rumbar Pirates' doctor was killed in the attack, the survivors were slowly wasting away. Knowing that he had eaten the Yomi Yomi no Mi, Brook suggested to his crew that they should play one last song that would be recorded on a Tone Dial that they had previously bought from a merchant. Since he would be revived after death, Brook promised them that he would take the Dial and play it for Laboon to hear. Overjoyed with Brook's proposal, the remaining Rumbar Pirates mustered what little strength they had and started singing their favorite song for the last time. Though joyful at recording their song, the remaining Rumbar Pirates slowly succumbed to the poison and died one after another. They each fell with smile on their faces until only Brook was left all alone. With a heavy heart, Brook continued playing all alone until he finally succumbed to the poison and died. After a year of searching, the soul of Brook found the Rumbar Pirates' ship and his body. Resurrected as a skeleton, Brook put his comrades' remains in coffins. However, Brook remained ever aware of his crew's inability to keep their promise to Laboon.

The Whale and the Straw Hats
Fifty years after the incident in the Florian Triangle, The Straw Hat Pirates meet up with Laboon as they enter the Grand Line themselves. There they rescue Laboon, from Mr. 9 and Miss Wednesday who are trying to kill him and use him as food for their village. They find out that in order to take care of the giant whale, Crocus has installed several things inside of Laboon including his own house floating in the stomach acid. They are told the story of the Rumbar pirates and how they never came back. Crocus believed they became scared and left through the Calm Belt, only to be killed there. In order to stop Laboon from hurting himself, Luffy draws his Jolly Roger on his scars and tells him he will come back one day.

The Rumbar Rest in Peace
It has recently been revealed to Brook, by Luffy, that Laboon is alright. He continues to tell him that he is still waiting and that he has grown as large as a mountain. Hearing this, Brook bursts into tears. He then proceeds to find the Tone Dial in his skull and starts to play the recording made right before the crew died. The others join and Brook thinks of his promise to Laboon. In his mind he tells him to wait a little longer and then he will surely keep his promise and come back over that wall. He then stops the Tone Dial and says it is no longer used for reminiscing but to be brought to Laboon. Brook then asks to join Luffy's crew and is accepted. During this time Laboon roars out to Crocus, who remarks that Laboon is unnaturally happy that day.

Franky later makes a tombstone on Thriller Bark to hold all of the coffins of the Rumbar Pirates. Brook remarks that it is suiting that his crew would be buried at Thriller Bark since it comes from their homeland of the West Blue.

Crew Members
The first captain, Yorki, and some other crewmen became ill and died while trying to return through the Calm Belt. The rest of the crew died in battle within the Florian Triangle, all save Brook (who was revived) and the baby Island Whale Laboon (who was left behind at Reverse Mountain).

Crew Abilities
The crews strength took them far into the Grand Line, however they met their end upon entering into the Florian Triangle. It is unknown who killed them, only that they died fighting a foe they could not win against. As pirates, they were all prepared to die anytime, and as such, did not fear death. They only regretted that they must die before reuniting with Laboon.

Also it seem that many of them are very good at playing musical instruments. Brook even claims he can play all kinds of instruments, showing the ability to play at least violin, piano and guitar.

Furthermore, their sole surviving member (of sorts), Brook, was skilled enough to terrorize Thriller Bark along with its many undead inhabitants all on his own.

First Ship
The first ship used by the Rumbar Pirates was relatively regular sized, and made its debut in a flashback in Chapter 103 and Episode 63. It had the bull skull from the Rumbar Pirates' Jolly Roger as its figurehead. Originally in the manga and anime, the figurehead was maneless. Later it was given a mane. In the anime also, it was initially colored brown. Later it was colored green.

The ship was used by the Rumbar Pirates for many of their adventures. From their escapades in their home sea of West Blue to their journey across the first half of the Grand Line. When Yorki and some of the other Rumbar Pirates got infected however, they had no choice but to take the quarantined ship and regretfully leave Brook and the remaining crew. In hopes that something could be done, they tried to steer the ship out of the Grand Line by passing through the Calm Belt. There was a report that identified the ship leaving the Grand Line via the Calm Belt. Due to not knowing the real reason why the ship was leaving, Crocus assumed that the Rumbar Pirates were abandoning Laboon.

Second Ship
The second vessel the Rumbar Pirates used after they lost half of their crew made its debut when Brook himself used it to sail around the Florian Triangle. Due to Brook being a pirate it's his pirate ship, although Luffy's crew refers to it more as a ghost ship because of its haunted appearance. The vessel is around 50 years old. It is a large vessel at least ten times the Thousand Sunny's size, and unlike the first ship, had no figurehead. While the ship was badly damaged and worn due to time, it was repaired by Franky and was given to and is used by the Rolling Pirates and the rest of the Thriller Bark Victim's Association as Brook decided to finally join the Straw Hat crew aboard their own ship.

While the Jolly Roger on the ship's sails is the Rumbar Pirates' Jolly Roger, in the anime however, the ship is shown with a completely different Jolly Roger when it originally appeared and in the episodes following after it.

This error originates from how the design of the Jolly Roger was slowly revealed in the manga. In the scenes in the manga before Brook revealed himself as a Rumbar Pirate, the Jolly Roger was originally obscured by fog. This was done in order to not reveal prematurely Brook's true identity. Because the episodes where his ship has a different Jolly Roger were made before his revelation, the animators used a different Jolly Roger based on what could be made out from the manga at the time.

Though this error is prevalent in most of the episodes before Brook's revelation, a later episode in the anime, that was made after Brook's revelation in the manga, corrects the error by showing a Jolly Roger like the one in manga though albeit obscured by fog.

Trivia

 * The name of the crew appears to be a combination of two similar words in a pun. The first term, "Rumba", refers to a family of music rhythms and dance styles that originated in Africa. The second term, "Lumbar", is a section of the body around the abdomen, known for the bones and spinal cord that exist there as part of the skeletal system. Due to the love of the music by the crew as well as due to Brook himself (who's skeleton, including his lumbar bones, are exposed due to the affect of the Yomi Yomi no Mi), it is presumed the two words were combined to define the name of the crew.
 * Despite being wiped out for about half-a-century, the Marines kept track of the crew's information, as they managed to trace Brook's connections based on the past bounty poster.