The QY70/100 models have a linear 16-track sequencer and an 8-track pattern sequencer, allowing simultaneous use for complex compositions.

The pattern sequencer uses Yamaha's "Accompaniment" engine with specific track formats: Drum1, Drum2, Perc, Bass, and Chord 1-4, which can automatically transpose to chords.

The Yamaha QY20 is recognized for its ability to store multiple parts and thousands of notes, suiting those looking for song- and part-based sequencing.

The QY20's sequences are stored internally, allowing them to play on any synth connected, provided it's on the same MIDI channel.

Owners note the QY20's internal battery might need replacing, with a message on the screen indicating its status.

Changing the internal battery requires basic soldering skills and tools, including de-soldering braid, a soldering iron, leaded solder, and a replacement battery and holder.

Owners encountering power issues may need to investigate the MAX680 IC, a voltage converter, for potential repair needs.

The QY70 can be used to sequence multiple MIDI instruments with its 16 available MIDI channels, making it a versatile MIDI controller.

The QY20 can serve as a standalone MIDI sequencer for synth modules, perfect for users seeking a computer-free setup.

Users suggest the QY70's screen is small, requiring extensive menu navigation, but it's packed with useful editing features.

The QY70's interface is considered archaic, with some programming tasks being tedious, but basic skills can be learned in a few hours.

Some users struggle with non-functional units due to previous modifications like circuit bending, requiring a detailed inspection and understanding of the internal circuitry.

A white wire soldered to pin 6 of the MAX680 IC suggests a past repair attempt, indicating possible issues with the IC receiving the required voltage.

The QY20 is suggested as a good starting point for those exploring older sequencers from the mid-1980s onwards, despite the primitive data entry methods.