This article has been updated in 2023 to tell you more ways to make microtonal music with software synthesisers.

Many software plugins (VST, AU, RTAS etc.) allow you flexible control over intonation, which can be used to create music with any tuning system you like. There is no one single method, so depending on your synth, you’ll be able to get at those microtones with one or more of the following:

• Synth that supports reading in a ‘tuning file’ from the hard disk. (Usually a .tun or .scl file).
• Synth that supports MTS-ESP. (To be used with an MTS-ESP master plugin, more on that later).
• Synth that supports MPE (MIDI Polyphonic Expression), which means each note can have pitch bend applied independently of other playing notes.
• Synth that understands received MTS (MIDI Tuning Standard) data as MIDI SysEx messages.
• Synth that allows direct data input into the synth interface.

Plugins that don’t support any of the above may still be tuned by systematically using the pitch bend, however this only works for monophonic parts (unless you use multiple instances of the same plugin).

To find out how your synth can be microtuned, look it up in this table of microtunable software plugins. From there you’ll also find a few free VST downloads to experiment with.

Using tuning files: .tun .scl and others

If your softsynth loads .tun files (AnaMark, Linplug instruments, Omnisphere, etc.) then check out my tutorial on how to create a .tun file using Scala.

If you’re using something like Surge XT, PianoTeq, ZynAddSubFX, Plogue chipsounds or Garritan Personal Orchestra 4 (amongst others), these synths can load .scl files. It’s simple to find this kind of file for download on the internet, and they are easily created using Scale Workshop.

Using MTS-ESP

Synths that support MTS-ESP will need an MTS-ESP master plugin to control the tuning. Some examples of MTS-ESP master plugins:

• MTS-ESP Suite
• Entonal Studio
• Infinitone DMT
• There are various others

Using MIDI Tuning Standard (MTS)

The MTS never really took off in the same way that MTS-ESP and MPE is taking off in recent years. In my experience, a lot of the MTS-capable synths are hardware and not software.

Synths such as Xen-Arts’ instruments can be tuned by using MIDI tuning messages. Such data can be generated by software like Scala, alt-tuner, CSE or LMSO. Then, the data is either sent to the synth in real-time or dumped into a file to be read later.

One approach is to include the MIDI tuning messages in a MIDI track within your DAW. The MIDI track should output to all tracks which contain an instance of the synth. This approach works well in a DAW like Reaper, which has powerful routing. Unfortunately this approach won’t work in Ableton Live or FL Studio, because these DAWs filter out all SysEX data, thereby stopping your synth from receiving the MIDI tuning messages.

Another approach is to create a MIDI tuning dump. This is a .mid file containing only MIDI tuning messages. Some synths, such as XenFont, IVOR, and Xen-FMTS 2, conveniently import this kind of file. The tuning dump can also be created using Scala.

[Note: Xen-Arts synths are no longer available]

Synths that support direct note input

Direct note input is not a common feature of synths, but there are a few:

• Surge XT
• Pianoteq
• ZynAddSubFX

TLDR: just tell me the best free microtonal synth I should use

Surge XT

Further reading

• DAWs article on the Xenharmonic Wiki
• List of Microtonal Software Plugins article on the Xenharmonic Wiki