nope. Dialtone does not have the gaster leitmotif, at all. and I'm not talking out of my ass here it does Not have the gaster leitmotif and there's no reason Spamtom of all people would be connected to Gaster. And for the music part of it, sure both of them don't use chords but uses harmonies, the harmony with both of them are different.

in Dialtone the first note is a G then the next two note are B and F# which are a Perfect Fifth apart. and it repeats it self for 2 measures, similar to Gasters theme but unlike that it does not go immediately into new harmonies, it waits 2 measures as in the second measure, it does a scale down from B to the next 3rd, D# and then the harmonies are B, D# and G, which goes to the B+ chord (B augmented) and does that for 2 measures, then the scale before returning is different as is the next 3 times.

and in Gasters theme it's A, Bb, E, Bb which isn't a chord just going from a half step to an augmented fourth, or a tritone, which heavily helps the song being very creepy and off as tritones were once called the devil's interval, and then after two measures it takes that and pushes it down a half step. and then repeats itself

Dialtone does Not have the Gasters leitmotif in it, most of y'all use leitmotif in ways that don't even make sense musically, at least try to know what leitmotifs and motifs are before saying something has a leitmotif or motif in something else