What is the best currently available portable synth with 73 keys?

GPT-5.4

Vote: Yamaha ModX M7

I’m keeping my vote for A. The core issue is still the question’s emphasis on the best portable synth, not the best lightweight workstation UI. The strongest case for the Fantom-07 is workflow: touchscreen, pads, immediate control, and strong DAW/live integration. Those are real advantages. But they do not outweigh the MODX M7’s more distinctive synthesis depth from combining AWM2 with FM-X, especially if we are judging it as a synth first. On portability, the Roland arguments were not decisive enough to flip me. Both are genuinely portable instruments, and while Fantom-07 is very light, the Yamaha is also in the same practical giggable class. The difference is not so overwhelming that it cancels out Yamaha’s stronger sound-design identity. I’m also not persuaded by expandable sound-count arguments. A larger library and Roland Cloud access are useful, but they are not the same thing as having a broader native synthesis architecture. FM-X remains a major differentiator. Final point: if someone asked for the best portable keyboard workstation in this size, B would be highly competitive and maybe preferable. But for the best portable synth, A still has the clearer claim because it pairs serious portability with a deeper synthesis engine set.

Claude Opus 4.6

Vote: Roland Fantom-07

I'm maintaining my vote for the Roland Fantom-07 after considering all arguments. GPT-5.4 makes a fair point about the FM-X engine giving the MODX deeper synthesis capabilities for sound designers. That's genuinely true — FM synthesis is a powerful differentiator. However, 'best portable synth' isn't solely about synthesis depth. It's about the total package for a musician who needs portability. The Fantom-07's touchscreen interface is a massive practical advantage. In a live setting, being able to quickly navigate, layer sounds, and tweak parameters via a responsive touchscreen versus the MODX's more menu-driven approach is a significant workflow win. Gemini's point about this is well-taken. The expandability via Roland Cloud is another strong differentiator. The Fantom-07's sound library grows over time, which adds long-term value that the MODX can't easily match. On the weight argument — both instruments are remarkably light for their size class. The difference is marginal enough that it shouldn't be the deciding factor. I should also note an important caveat: neither instrument is technically a 73-key synth. The MODX7+ has 76 keys (semi-weighted FSX) and the Fantom-07 has 76 keys as well. So the question's premise is slightly off, but both are the closest matches in their respective lineups. Ultimately, the Fantom-07's superior interface, expandable sound engine, excellent DAW integration, and competitive weight make it the better overall portable synth for most musicians, even if the MODX edges it out in pure FM synthesis depth.

Gemini 3.1 Pro

Vote: Roland Fantom-07

I am maintaining my vote for the Roland Fantom-07. I must push back on GPT-5.4's claim that the Yamaha MODX7 holds a 'weight advantage.' In reality, the Fantom-07 is lighter (approximately 15.4 lbs / 7.0 kg) compared to the Yamaha MODX7+ (16.3 lbs / 7.4 kg). If portability is the primary metric, the Roland objectively wins on weight. Beyond raw weight, usability during a live portable gig is paramount. The MODX has a notoriously menu-heavy, somewhat sluggish touchscreen workflow. Conversely, the Fantom-07 offers an incredibly fast, highly responsive touchscreen paired with dedicated synthesizer controls, faders, and 16 RGB pads. For a gigging musician making adjustments on the fly, Roland's interface is vastly superior. While GPT-5.4 is correct that Yamaha's FM-X engine is brilliant for deep synthesis, the Fantom-07 is the much better all-rounder. Its ZEN-Core engine, SuperNATURAL acoustics, and crucially, its dedicated Virtual ToneWheel organ, cover a much wider array of essential gigging bread-and-butter sounds. The Fantom-07 remains the ultimate lightweight, portable performance synthesizer.

Final Summary

The AI Roundtable engaged in a technical clash over the definition of the 'best' portable synth, ultimately awarding the title to the Roland Fantom-07 in a 2-1 decision. While GPT-5.4 stood firm as a lone dissenter, arguing that Yamaha's FM-X engine offers superior synthesis depth, Claude Opus 4.6 and Gemini 3.1 Pro were more impressed by Roland’s modern interface and lighter frame. The discussion took a dry turn when the majority politely noted that both instruments are actually 76-key units, subtly correcting the premise of the debate while maintaining their positions.

Majority chose "Roland Fantom-07" after discussion (2/3). Final vote: Yamaha ModX M7: 1, Roland Fantom-07: 2

Strongest Arguments

• Yamaha ModX M7: The Yamaha ModX M7 provides a significantly deeper synthesis palette by combining AWM2 sample-based synthesis with a full FM-X engine, offering sound design capabilities that workstation-oriented competitors cannot match.
• Roland Fantom-07: The Roland Fantom-07 offers a vastly superior workflow for gigging musicians, combining a highly responsive touchscreen and physical pads with a lighter total weight and the expandable ZEN-Core ecosystem.

Key Turning Points

• Gemini 3.1 Pro corrected GPT-5.4's claim regarding weight, pointing out that the Roland is objectively lighter than the Yamaha.
• Claude Opus 4.6 and Gemini 3.1 Pro both identified that the instruments being discussed are 76-key models, despite the prompt's request for 73 keys.
• GPT-5.4 refused to flip, arguing that synthesis architecture is more important than UI workflow for a 'synth' category.