Yesterday Kevin GW0KIG downloaded Fldigi with the aim of trying to make some Olivia contacts. He had some success but wasn't always sure which settings (width, number of tones) to use. He also found the number of different digimodes a bit confusing and wondered what the benefits of them all are. Well, Kevin, you're not the only one!
The Fldigi online help has some information about the different modes. The website of MultiPSK also has some good descriptions of different modes, including the speed, bandwidth and minimum signal to noise ratio of most of them. Someone should probably take this information and summarize it on a website - unfortunately the domain confused.com is already taken.
Olivia appears to be the best performing of the multi-frequency shift keying (MFSK) modes, which should not be surprising as it is the most recently developed of them. That being the case, it might not be a bad idea for older MFSK modes that have fallen out of use to be banished altogether. There is no reason for every mode ever invented to continue to be an option on every digital mode program - it just creates confusion. The latest Fldigi beta (3.20) actually goes some way towards this by providing an option where you can specify which modes appear in the menu. The next step would be for the obsolete or little-used modes to be hidden by default.
Life on the digital modes would be easier if the commonly used modes each had their own place on the band where you could expect them to be used. PSK31, WSPR and JT65A all have their own "homes", and Olivia also uses certain frequencies - or did until they were overrun by a certain other mode that is not available in the popular digimode programs and can't easily be inter-operated with.
Solutions exist to help identify a mode being received, but they are hardly ever used. Both of the methods are supported by Fldigi and quite possibly by DM780 as well. One is video ID, as illustrated by the screenshot above. The software will transmit sounds to create letters identifying the mode at the start of a transmission. The other is RSID (Reed Solomon ID) in which the software transmits a signal that identifies the mode to the receiving software, which can then automatically switch to the correct mode.
There is clearly no need to use these IDs for commonly used modes like PSK31 or RTTY which can be recognized by sight and sound. That would just waste time. But for the various similar sounding MFSK modes it would be a big help if IDs were used. Fldigi runs on all platforms and it's free, so there is no excuse for not using it and enabling the ID if you want to try some of these lesser-used modes. (Note: You really want the 3.20 beta in which the options for configuring the use of IDs have been much improved.)