(I was going to mention this in my last post on gaming prep & workflow, but it really is its own topic)
I have spent hours hand-picking music for my in-person games and I consider that time well spent - everyone comments on the atmosphere during the game! This is the kind of work that continues to pay off, since the same playlists can be used multiple times (with periodic updates to keep them fresh). That kind of work is useful prep. Plenty of other things, aren't.
If you use Spotify, maybe that works for you, I don't know. I still use mp3s on my phone because I grew up with Napster. For my current in-person game I have a wilderness playlist and a dungeon playlist which have each grown from about 2 hours of music to -- checks notes -- over 6 and 7 hours respectively, more than enough to run a session and not hear any repeats.
It has taken me a LONG time to build these playlists because I have very stringent requirements for in-game music, which I will try to outline here for your edification and amusement:
Rule 1 - Minimal Dynamic Range
When you first decide to play music during your games, you might run for the music of your favourite films. The problem is that most film soundtracks are written & produced just like classical music with much broader dynamic range than modern popular music: from near-silence to huge crescendos. This works during a movie but is absolutely insufferable to listen to even at home alone, when I'm trying not to turn my stereo's volume knob every goddamn minute.
Most 'modern classical' compositions are simply way too over-the-top to work as background music anyway. Big orchestra hits, swells, violins attacking like swarms of bees, timpanis crashing... I'm trying to have a conversation here! Hans Zimmer is really bad for this. During a game this will amount to quiet sections being totally inaudible while everyone is talking, then conversation getting interrupted by a blast of sound. A non-starter.
What you want is a constant volume level so that you can set it and forget it. Your game music must be quiet enough that it doesn't impinge on everyone talking & nobody has to raise their voice, loud enough that it can actually be heard a little bit.
This is actually a very narrow band!
An additional oft-overlooked consideration with this rule is trying to find songs that are roughly volume matched to each other. I think Spotify or some other streaming services might do this for you? Just pay for premium because if I hear an ad during your game I'm strangling you.
Some examples of too much dynamics:
On the flip side, this track is consistent throughout. Howard shore is the GOAT but take care because not every song on this album is so cooperative.
Rule 2 - Not too 'song-like'
I used to play extreme metal or folk music during my games, I don't do that anymore. I avoid anything with drums and most guitars. This contributes to the background sense of the music - I don't want the players to really take notice except in rare instances. Strings, synthesizers, things like that are all fine. Even in ambient music there are percussive elements and these should be considered carefully, some can work as long as they don't sound like an actual drum kit.
Acoustic guitars can be OK, depending. Medieval instruments like a glockenspiel or something need to be chosen with care, as they can easily descend into terminal cheesiness. Anything with lyrics is right out, although some vocal chants or something might be okay.
Rule 3 - Not Easily Recognizable
The hardest one to do, depending on your gaming group. The first time a player says "Hey, isn't this from Lord of the Rings?!" you'll never make that mistake again. Everyone is now imagining the scene where Gollum finds the ring, instead of the damned hexcrawl you're trying to run. Pretty soon someone is doing a Gimli voice, someone else is telling the story of Viggo Mortensen breaking his toe and the game has gone completely off the rails.
Just don't do it! Skip Hollywood franchise films, blockbusters and things your players will know (I can't tell you what those will be, you have to know your players - a DM's work is never done).
Dig deeper and find stuff people haven't heard. This is where being into underground music really pays off (a rare circumstance indeed!). Call up your much cooler friends and ask them what they're listening to. Dig into anime from the '90s, foreign films, non-triple A videogames, or fire up Youtube and poke around for some new microgenre that hasn't been saturated to death yet.
Rule 4 - Not Too Much Variety
I stick to 3 or 4 artists for a particular themed playlist. This is not a hard rule. Since it's tough to find composers who have enough songs that fit my requirements, it ends up working out this way. I find creating strongly themed playlists works better - the players can feel the difference between different areas of the game world, different modes of play or even levels of danger!
Rule 5 - No Jazz!
No matter what Noisms says! (that article has some good stuff in it though)
Suggestions
Oh what, you want some songs that you should include, instead of a list of prohibitions? Okay, here are a few, you'd better thank me for bestowing my wealth of experience. I'm giving y'all the game here, so don't say I never did anything for you guys!
Remember, these are entire albums. You have to use the principles I just taught you to pick the appropriate songs from each!
There you go, no more excuses.
Now get back to your game, blogland!