You know what? You just can’t be sad while listening to funk.
It’s music with the sole purpose of making you want to dance, tap your head or foot, put you in a good mood. What it may lack in variety or ambition it makes up for in sheer good nature. This is part of what makes this album title funny; the entire album, and genre, of jazz-funk is the opposite of rage. 
Lettuce is a supergroup made up of jazz sidemen who get together every few years to record an album; they’ve done something like five albums in 20 years. It’s not an ongoing concern, just a way for musicians to jam together in a genre they all love. That genre is ’70s jazz-funk, and this album is full of cheerful, mostly instrumental three-minute blasts of joy.
Obviously, there’s a huge influence here from bands like Earth Wind & Fire, Average White Band, Parliament, and the funk periods of James Brown and Stevie Wonder; most are originals, with a take on Curtis Mayfield’s “Move On Up” appearing early in the proceedings. The sounds are so similar that you could fit a Lettuce song between any of those other bands on that playlist and not even realize you’d left the ’70s (I tested this theory on my Spotify funk-jazz station while I was cooking risotto the other day, in case you were curious).
Listening to them all back to back gets a bit tiresome, as there’s not much variety or vocals to be found, but the album breezes by on charm and horns. If you’re looking for a highlight, I guess “Salute” would be the best of the bunch, featuring a tricky horn riff over a swaggering beat and some indistinguishable spoken voices and clanking dishes in the background, meant to evoke a strut down a New Orleans street.
This album has a specific purpose, and it’s pretty entertaining as far as side projects go, though if you’re looking to get into funk, best to go with the originals. The guys in Lettuce (as in, let us play) love those originals too and are only too happy to pay tribute. If that doesn’t sound like fun, well, just listen to a couple of the songs and you’ll be smiling in no time.