We've gathered every free 4-operator FM bank we could find on the web. We combined them all, removed all the duplicates, and then separated them back into banks. The result is 82 banks of 32 patches, or over 2600 patches in total.
Are they categorized or anything? Nope, just straight alphabetical. Sorry, we couldn't do all the work for you. However, there is a text file containing the name of every patch and which bank you can find it in.
Are they all good? Absolutely not. Not even close. We've heard enough cheesy clavs to last a lifetime.
What kind of patches can I find? Some pretty standard, mostly old-school, bread and butter FM patches. Many sound very dated, but if you explore the lower octaves, you can sometimes find some unintended interesting sounds. We added a folder for some classic and some of our favorites to help get you started.
What about some modern bass sounds? Nope, sorry. We've listened to just about all them and you're not going to find too many that you'd consider a talking/robot/neuro/vowel bass, etc. Most of the old synths these patches were made on probably couldn't create the more modern bass sounds since they mostly rely on automation and macros.
What synths will these work with? We could only test with the Yamaha TX81Z and FM8 and they work with both of these. You should be able to load them in earlier Yamaha 4 OP synths like the DX21 ad DX100, but these banks contain 32 patches and all the earlier generation 4 OP synths seem to only load 24 per bank. They will probably work with other software synths that load 4 OP sysex files.
How long did this take you? Probably too long. However, we did make heavy use of MidiQuest11 which helped greatly in transferring back and forth from our TX81Z, pooling all the patches and eliminating duplicates. There may be some sounds that are very similar or named the same, but according to MQ11 there are 0 exact duplicates. If you already own MidiQuest, we've included the library file with all the patches.